Lens barrel, lens driving apparatus, camera, and mobile information terminal

ABSTRACT

A lens barrel capable of accurately detecting a position of a retractable lens retaining frame. A frame female member for rotating a frame around a lead screw and driving the frame in forward and backward directions along the lead screw is formed with a T-shared protruded member as a detected portion located at a position opposite a rotation-preventing projection. The T-shared member structures a position of the frame together with a transmissive photo-interrupter, to decide a reference position in a retracted state of the frame and for an optical axis entrance completed position of the frame at a time when a transition has changed from a retracted state to a photographable state, and detects a distance from the reference position of the frame or a position of the frame in the photographable state in which a focal distance during wide-angle photographing and telephoto photographing is changed.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is based on and claims priority benefit from Japanese Patent Application No. 2005-063318, filed Mar. 8, 2005, the disclosure of which is hereby incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention generally relates to a lens barrel in which each lens group is collapsed in one form and each of the lens groups is extended out to a predetermined position to be used in another form. More particularly, the invention relates to a lens barrel suitable for a zoom lens capable of changing a focal distance by relatively moving a plurality of lens groups, a lens driving apparatus, a camera, and a mobile information terminal using the lens barrel.

BACKGROUND ART

Conventionally, in an imaging device such as a digital camera, with advance in a high performance of a lens barrel having a zoom lens function capable of changing a focal distance, or miniaturization of the imaging device according to the user's demand, there has been increasingly used a lens barrel in which a plurality of lens groups is collapsed when photographing is not carried out. Furthermore, because of the demand for not only simple reduction in dimension, but also further reduction in thickness, it is now important to reduce the thickness of the lens barrel in a collapsed position to the maximum extent.

As a technology to cope with the demand for reduction in thickness of the lens barrel, there has been used a lens barrel in which a lens cylinder retaining therein a plurality of lens groups is collapsed into the imaging device when not in use, and one of the lens groups is retracted out of an optical axis of the lens groups when the lens groups are collapsed.

A technology for retracting one of lens groups out of an optical axis is disclosed in, for example, JP 2003-315861A (Patent Document 1) and JP 2003-149723A (Patent Document 2). According to the structure disclosed in each of the Patent Documents 1 and 2, a mechanism is employed wherein an optical axis of a lens group retained by a retractable lens retaining frame is estranged from an optical axis of other lens group when the lens groups are collapsed and the optical axis of the lens group of the retractable lens retaining frame is made to coincide with the optical axis of other lens group when the photographing is being carried out. Since one of a plurality of lens groups disposed on the optical axis is retracted out of the optical axis when the lens groups are collapsed, the entire dimension of the lens barrel in a direction of the optical axis can be reduced, so that the thickness of the imaging device is reduced.

Note that, in the structure disclosed in Patent Documents 1 and 2, the lens retracted out of the optical axis is actually positioned within a lens cylinder provided in the lens barrel to retain therein the lens groups, even after the lens is retracted.

However, according to a structure of a conventional technology such as those disclosed in the Patent Documents 1 and 2, there has been a problem that it is difficult to accurately grasp a change in positions of the retractable lens retaining frame when the optical axis of the lens group retained by the retractable lens retaining frame is made to coincide with or estranged from the optical axis of other lens group in a transition from a collapsed state to a photographing state or from the photographing state to the collapsed state. There has been also a problem that it is difficult to accurately grasp displacement of the retractable lens retaining frame in an optical axis direction coaxial with the optical axis of other lens group when the photographing is being carried out. Further disadvantage of the conventional technology is that a mechanism for detecting the position of the retractable lens retaining frame in a direction estranging from the optical axis of other lens group and/or a mechanism for detecting the position of the retractable lens retaining frame in the optical axis direction coaxial with the optical axis of other lens group, become complicated.

DISCLOSURE OF THE INVENTION

The present invention has been made in view of the above-mentioned circumstances, and therefore, at least one objective of the present invention is to provide a lens barrel capable of detecting a position of a retractable lens retaining frame with high accuracy, a lens driving apparatus, a camera, and a mobile information terminal using the lens barrel.

To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a lens barrel, comprising: a) a plurality of lens groups each having at least one lens; b) a plurality of lens retaining frames each retaining corresponding one of the plurality of lens groups; c) a telescopic cylinder containing therein the plurality of lens groups and the plurality of lens retaining frames; d) a lens retaining frame driving device configured to drive at least one of the lens retaining frames; at least one portion of the plurality of lens groups being collapsed to store the plurality of lens groups in a collapsed state and at least one portion of the plurality of lens groups being moved toward a subject in a photographable state, the plurality of lens retaining frames including a retractable lens retaining frame configured to retain and retract at least one of the plurality of lens groups to a retracted position substantially out of the telescopic cylinder in the collapsed state and configured to move the corresponding at least one of the plurality of lens groups from the retracted position to a photographing position in the photographable state such that an optical axis of the corresponding at least one of the plurality of lens groups substantially coincide with an optical axis of the other lens group of the plurality of lens groups in order that all of the plurality of lens groups be substantially aligned on the same optical axis; and e) a position detector configured to detect a change in a position of the retractable lens retaining frame in the collapsed state and in the photographable state, the retractable lens retaining frame including a cam portion configured to change a position of the retractable lens retaining frame between the retracted position which is substantially out of the telescopic cylinder and which is distant from the optical axis of said the other lens group, and the photographing position in which the optical axis of the corresponding at least one of the plurality of lens groups retained by the retractable lens retaining frame is positioned substantially on the optical axis of said the other lens group and in which the retractable lens retaining frame is moveable in a direction substantially coaxial with the optical axis of said the other lens group, so as to detect, based on an amount of a displacement of the retractable lens retaining frame in the direction substantially coaxial with the optical axis of said the other lens group, a displacement of the retractable lens retaining frame in a direction in which the optical axis of the corresponding at least one of the plurality of lens groups retained by the retractable lens retaining frame approaches and separates away from the optical axis of said the other lens group between the collapsed state and the photographable state, and a displacement of the retractable lens retaining frame in the direction substantially coaxial with the optical axis of said the other lens group in the photographable state, the lens retaining frame driving device including a lead screw configured to advance and retreat the retractable lens retaining frame in a direction substantially extending parallel with the optical axis of said the other lens group, and a female screw member screwed on the lead screw and capable of being advanced and retracted by rotation of the lead screw in an axial direction of the lead screw which extends substantially in parallel with the optical axis of said the other lens group, the female screw member including a contact portion configured to contact with the cam portion to change the position of the retractable lens retaining frame between the retracted position and the photographing position by the rotation of the lead screw, and the position detector including a detected portion provided on the female screw member so as to detect the position of the female screw member in the axial direction at the time of the rotation of the lead screw, and a detecting portion arranged in an area of movement of the detected portion for detecting a displacement of the detected portion in the axial direction.

Following are preferred embodiments (1) to (6) of the lens barrel according to the present invention. Any combinations thereof may be considered to be preferred ones of the present invention unless any contradictions occur.

(1) The position detector is configured to generate a reference signal indicating that the retractable lens retaining frame is located at the retracted position so as to change a state of the retractable lens retaining frame from the collapsed state to the photographable state, before moving the retractable lens retaining frame from the retracted position to the photographing position so as to substantially coincide the optical axis of the corresponding at least one of the plurality of lens groups retained by the retractable lens retaining frame with the optical axis of said the other lens group. (2) The position detector is configured to generate an entering completed signal indicating that entering of the optical axis of the corresponding at least one of the plurality of lens groups retained by the retractable lens retaining frame on the optical axis of said the other lens group from the retracted position to the photographing position has completed, after the state of the retractable lens retaining frame has changed from the collapsed state to the photographable state. (3) The position detector is configured to output a positional reference signal in an optical axis direction so as to displace the retractable lens retaining frame in the direction substantially coaxial with the optical axis of said the other lens group for performing photographing, after the optical axis of the corresponding at least one of the plurality of lens groups retained by the retractable lens retaining frame has approached on the optical axis of said the other lens group from the retracted position to the photographing position. (4) At least one optical element located nearer to an image plane in the lens barrel than the retractable lens retaining frame is included, and wherein the position detector permits movement of the optical element after generating the entering completed signal of the retractable lens retaining frame at the time when the state of the retractable lens retaining frame has transited from the collapsed state to the photographable state. (5) The detected portion is substantially in an alphabet T configuration. (6) The detected portion is substantially in an alphabet L configuration.

The present invention also provides a lens driving apparatus, comprising the lens barrel according to any one of the lens barrel mentioned above.

The present invention further provides a camera, comprising the lens barrel according to any one of the lens barrel mentioned above.

The present invention further provides a mobile information terminal, comprising the lens barrel according to any one of the lens barrel mentioned above.

It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.

EFFECT OF THE INVENTION

In the lens barrel according to the present invention, at least one portion of the plurality of lens groups, each having at least one lens, is collapsed to store the plurality of lens groups in the collapsed state and at least one portion of the plurality of lens groups is moved toward the subject in the photographable state.

In order to attain the movement between the collapsed state and the photographable state as well as to attain miniaturization, the lens barrel according to the present invention is provided with the plurality of lens retaining frames each retaining corresponding one of the plurality of lens groups, the telescopic cylinder containing therein the plurality of lens groups and the plurality of lens retaining frames, and the lens retaining frame driving device configured to drive at least one of the lens retaining frames.

The plurality of lens retaining frames includes the retractable lens retaining frame configured to retain and move at least one of the plurality of lens groups, so that the lens barrel according to the present invention is possible to retract at least one of the plurality of lens group to the position more out than the telescopic cylinder or outside of the maximum outer diameter of the telescopic cylinder in the collapsed state and to position the corresponding at least one of the plurality of lens groups retained by the retractable lens retaining frame such that all of the plurality of lens groups are substantially aligned on the same optical axis.

The lens barrel including the retractable lens retaining frame is detectable of the displacement of the retractable lens retaining frame in the direction in which the optical axis of the corresponding at least one of the plurality of lens groups retained by the retractable lens retaining frame approaches and separated away from the optical axis of other lens group between the collapsed state and the photographable state, and the displacement of the retractable lens retaining frame changing in the direction substantially coaxial with the optical axis of other lens group in the photographable state, by the displacement amount of the retractable lens retaining frame in the direction substantially coaxial with the optical axis of other lens group.

In addition, in order to switch over from the collapsed state to the photographing state and from the photographing state to the collapsed state, the retractable lens retaining frame is formed with the cam portion for changing the position of the retractable lens retaining frame between the retracted position which is substantially out of the telescopic cylinder and which is distant from the optical axis of other lens group, and the photographing position in which the optical axis of the corresponding at least one of the plurality of lens groups retained by the retractable lens retaining frame is positioned substantially on the optical axis of other lens group and in which the retractable lens retaining frame is moveable in the direction substantially coaxial with the optical axis of other lens group.

Moreover, the lens retaining frame driving device is provided with the lead screw configured to advance and retreat the retractable lens retaining frame substantially in parallel with the optical axis, and the female screw member screwed on the lead screw to be capable of being advanced and retracted by the rotation of the lead screw in the axial direction of the lead screw.

The female screw member is provided with the contact portion which contacts with the cam portion to change the position of the retractable lens retaining frame between the retracted position and the photographing position by the rotation of the lead screw.

In addition, the position detector, which detects the change in the position of the retractable lens retaining frame in the collapsed state and in the photographable state, includes the detected portion provided on the female screw member for detecting the position of the female screw member in the axial direction, which is substantially in parallel with the optical axis, when the lead screw rotates. The position detector also includes the detecting portion arranged in the moving area of the detected portion in order for detecting the displacement of the detected portion in the axial direction.

Therefore, when the lead screw is rotated and thus the female screw member moves in the axial direction of the lead screw, the contact portion of the female screw member contacts with the cam portion, and thereby, it is possible to change the position of the retractable lens retaining frame having the cam portion from the retracted position to the photographing position, to move the retractable lens retaining frame forward and backward in the optical axis direction in the photographing position, and to return the retractable lens retaining frame from the photographing position to the retracted position.

In addition, the detected portion of the female screw member is configured to be detected by the detecting portion. Hence, it is possible to accurately detect that the retractable lens retaining frame is at the retracted position, the retractable lens retaining frame is in the state of changing from the retracted position to the photographing position, the photographing position of the retractable lens retaining frame in the photographable state, the retractable lens retaining frame is in the changing state from the photographing position to the retracted position, and so on, based on the position at which the detected portion is located.

Therefore, it is possible to detect changes in a state in the lens barrel promptly and accurately, and hence, operation from activation of a device installed with the lens barrel according to the present invention to completion of photographing can be promptly carried out to improve ease of use.

Here, coinciding of the optical axis of the lens group retained by the lens retaining frame with the optical axis of other lens group within the plurality of lens group and separating of the optical axis of the lens group retained by the retaining frame from the optical axis of other lens group may be attained by a structure which swings around a center point provided with the retractable lens retaining frame. Alternatively, a mechanism which allows the retractable lens retaining frame to enter into and evacuate from the optical axis of other lens group in a direction perpendicular to the optical axis of other lens group may be employed.

Also, according to one aspect of the lens barrel according to the present invention, the reference signal indicating that the retractable lens retaining frame is located at the retracted position is generated by the position detector so as to change the state of the retractable lens retaining frame from the collapsed state to the photographable state, before moving the retractable lens retaining frame from the retracted position to the photographing position for substantially coinciding the optical axis of the corresponding at least one of the plurality of lens groups retained by the retractable lens retaining frame with the optical axis of other lens group. Therefore, it is possible to determine reference time for the retractable lens retaining frame to change from the retracted position to the photographing position. Since the number of rotation of the lead screw and a feeding pitch of the female screw member are previously known, it is possible to accurately grasp the position of the retractable lens retaining frame from the number of rotation of the feed screw and an amount of feeding of the pitch of the female screw member after elapse of the reference time.

According to one aspect of the lens barrel according to the present invention, the position detector generates the entering completed signal indicating that entering of the optical axis of the corresponding at least one of the plurality of lens groups retained by the retractable lens retaining frame on the optical axis of other lens group from the retracted position to the photographing position has completed, after the state of the retractable lens retaining frame has changed from the collapsed state to the photographable state. Therefore, it is possible to accurately grasp the position of the retractable lens retaining frame in the optical axis direction at the time of the generation of the entering completed signal, so that it is possible to obtain a focusing position in the photographing, accurately.

According to one aspect of the lens barrel according to the present invention, the position detector outputs the positional reference signal in the optical axis direction so as to displace the retractable lens retaining frame in the direction substantially coaxial with the optical axis of other lens group for performing photographing, after the optical axis of the corresponding at least one of the plurality of lens groups retained by the retractable lens retaining frame has approached on the optical axis of other lens group from the retracted position to the photographing position. Therefore, it is possible to accurately detect the position of the retractable lens retaining frame in the optical axis direction.

According to one aspect of the lens barrel according to the present invention, at least one optical element (for example, a lens) located nearer to the image plane in the lens barrel than the retractable lens retaining frame is further provided, and the position detector permits the movement of the optical element after generating the entering completed signal of the retractable lens retaining frame at the time when the state of the retractable lens retaining frame has transited from the collapsed state to the photographable state. Therefore, it is possible to prevent an interference of the optical element with the retractable lens retaining frame, and also to shorten the time required from turning ON of the device having the lens barrel according to the present invention to a point of time in which lenses are protruded to be photographable, so that ease of use is attained.

Also, according to the present invention, the lens barrel comprises the plurality of lens retaining frames which include the retractable lens retaining frame configured to retain and retract at least one of the plurality of lens groups to the retracted position more out than the telescopic cylinder in the collapsed state and to move and position the corresponding at least one of the plurality of lens groups from the retracted position to the photographing position in the photographable state such that the optical axis of the corresponding at least one of the plurality of lens groups substantially coincides with the optical axis of other lens group of the plurality of lens groups in order that all of the plurality of lens groups are substantially aligned on the same optical axis. Therefore, it is possible to effectively minimize a size in the optical axis direction of the device installed with the lens barrel according to the present invention without extremely increasing a dimension within a plane transverse to the optical axis.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this description. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

FIG. 1 is a perspective view showing a structure of a main part of an optical system device including a lens barrel according to a first embodiment of the present invention with lens groups collapsed, as viewed from a subject.

FIG. 2 is a perspective view showing the main part of the lens barrel shown in FIG. 1, as viewed from an imaging plane.

FIG. 3 is a schematic perspective view showing a structure of a main part of the optical system device including the lens barrel in which a lens barrier is closed with the lens groups collapsed, as viewed from the subject.

FIG. 4 is a schematic perspective view showing the structure of the main part of the lens barrel shown in FIG. 3, as viewed from the imaging plane.

FIG. 5 is a schematic perspective view of the structure of the main part of the lens barrel in a state in which the lens barrier is opened in a photographing state with the lens groups extended, as viewed from the imaging plane.

FIG. 6 is a perspective view of the structure of the main part of the lens barrel in the photographing state with the lens groups extended, as viewed from the imaging plane.

FIG. 7 is a perspective view of a layout of a third frame, an impact preventing member, and a fourth frame in a state in which the lens groups are in a collapsed position, for explaining operations of the third frame which retains the third lens group and the impact preventing member, as viewed from the subject.

FIG. 8 is a perspective view of a layout of the third frame, the impact preventing member, and the fourth frame for explaining operations of the third frame, which retains the third lens group, and the impact-preventing member in the photographing state with the lens groups projected, as viewed from the subject.

FIG. 9 is a vertical cross sectional view showing, in an upper half and a lower half with respect to an optical axis, main parts of the lens groups, the lens retaining frames, and the various lens cylinders of the lens barrel in the photographing state in which the lens groups are extended, and in a collapsed state in which the lens groups are retired to be collapsed, respectively.

FIG. 10 is a schematic development elevational view showing a shape of cam grooves formed on a second rotary cylinder in a developed state.

FIG. 11 is a schematic development elevational view showing a shape of cam grooves formed on a cam cylinder in a developed state.

FIG. 12 is a schematic development elevational view showing a shape of cam grooves and key grooves formed on a first liner in a developed state with a helicoid omitted.

FIG. 13A is a schematic development elevational view showing a shape of cam grooves and key grooves formed on a fixed frame in a developed state with the helicoid omitted, FIG. 13B is a schematic development elevational view showing the shape of the cam grooves and the key grooves formed on the fixed frame in the developed state with the helicoid, and FIG. 13C is a perspective view showing an external appearance of a first rotary cylinder fitted to the helicoid.

FIG. 14A is a side view showing a structure of the third frame and its drive system, and FIG. 14B is a perspective view of FIG. 14A.

FIG. 15A is a schematic perspective view showing the structure of the third frame and its drive system, and FIG. 15B is a view schematically showing an assembled state of the third frame and its drive system.

FIG. 16A is a front view of the third frame part for explaining operation of the third frame, as viewed from the imaging plane, and FIG. 16B is a perspective view mainly showing a shutter part.

FIGS. 17A and 17B are schematic perspective views showing an exterior appearance and a structure of a camera according to a second embodiment of the present invention as viewed from the subject, wherein FIG. 17A shows a state in which a photographing lens is collapsed in a body of the camera, and FIG. 17B shows a state in which the photographing lens is projected or extended from the camera body.

FIG. 18 is a perspective view schematically showing the exterior appearance and structure of the camera of FIGS. 17A and 17B as viewed from a user.

FIG. 19 is a block diagram schematically showing a functional structure of the camera of FIGS. 17A and 17B.

FIG. 20A is a perspective view schematically showing a fourth frame and a main part of its drive system, and FIG. 20B is a perspective view showing the fourth frame and the main part of its drive system in which a part of those is omitted and seen from a different angle.

FIG. 21 is a block diagram schematically showing a structure of a drive control system.

FIG. 22 is a timing chart showing a sequence when the lens barrier is operated from a closed position to an opened position in an activation sequence.

FIG. 23 is a timing chart showing a sequence in which the lens barrier is operated from the opened position to the closed position in the activation sequence.

FIG. 24A is a table showing a reset sequence of the lens barrel, and FIG. 24B is a timing chart of HP signals.

FIG. 25 is a timing chart showing a storage sequence in a state in which the lens barrier is operated to close.

FIG. 26 is a flow chart showing a zoom sequence.

FIG. 27 is a timing chart showing a zoom sequence of zooming from the wide angle to the telephoto.

FIG. 28 is a timing chart showing a zoom sequence of zooming from the telephoto to the wide angle.

FIG. 29 is a perspective view showing a posture of the third frame in a retracted state.

FIG. 30 is a perspective view showing the posture of the third frame in the retracted state seen from a different angle.

FIG. 31 is a perspective view showing a mounted state of the fixed frame and the third frame.

FIG. 32 is a view showing a combined state of the third frame and a compression torsion spring.

FIG. 33A is a view showing a contacted state of a cam portion and an abutting portion of a third frame female screw member when the third frame is in the retracted state, and FIG. 33B is a view showing a contacted state of the cam portion and the abutting portion of the third frame female screw member when the third frame changes from the retracted state to the photographing state.

FIG. 34 is a view showing a positional relation of a T-shaped protruded member of the third frame female screw member and a photo-interrupter when the T-shaped protruded member passes between a light-emitting device and a light-receiving device of the photo-interrupter.

FIG. 35 is a view showing a positional relation of an L-shaped protruded member of the third frame female screw member and the photo-interrupter when the L-shaped protruded member passes between the light-emitting device and the light-receiving device of the photo-interrupter.

FIG. 36 is a timing chart representing a sequence when the lens barrel transits from the collapsed state to a telephoto state.

DESCRIPTION OF NUMERALS

-   11 First lens group -   12 Second lens group -   13 Third lens group -   14 Fourth lens group -   15 Shutter/aperture stop unit -   16 Solid-state image-sensing device -   17 First frame -   18 Cover glass -   19 Low-pass filter -   21 Fixed frame -   22 First rotary cylinder -   23 First liner -   24 Second rotary cylinder -   25 Second liner -   26 Cam cylinder -   27 Lineally-moving cylinder -   31 Third frame -   32 Third group main-guide shaft -   33 Third frame sub-guide shaft -   34 Third group lead screw -   35 Third frame female screw member -   36 Impact-preventing member -   37 Compression torsion spring -   38 Third-frame photo-interrupter -   41 Fourth frame -   42 Fourth frame sub-guide shaft -   43 Fourth frame spring -   44 Fourth frame main-guide shaft -   45 Fourth frame lead screw -   46 Fourth frame female screw member -   47 Fourth group photo-interrupter -   51 Zooming motor -   52 Third frame drive motor -   53 Fourth frame drive motor -   61 Barrier control member -   62 Lens barrier -   63 Barrier drive system -   71 Gear -   72 Gear -   73 Gear -   74 Gear -   81 Retainer plate -   82 Lens barrel base -   101 Image pickup lens -   102 Shutter release button -   103 Zoom lever -   104 Viewfinder -   105 Strobe light -   106 Liquid crystal display (LCD) -   107 Operating button -   108 Power switch -   109 Memory card slot -   110 Expansion card slot -   201 Photodetector -   202 Signal-processing unit -   203 Image-processing unit -   204 Central processing unit (CPU) -   205 Semiconductor memory -   206 Expansion card -   301 Barrier-operating element -   350 T-shaped protruded member (position detector) -   351 Photo-interrupter (position detector) -   501 Central calculation processing device -   502 Motor driver -   503 First and second frames DC motor -   504 First aperture stop motor -   505 Second aperture stop motor -   506 Shutter motor -   507 Third frame pulse motor -   508 Fourth frame pulse motor -   509 First and second frames photo-interrupter -   510 First and second frames photo-reflector -   512 Fourth frame photo-interrupter -   513 First and second frames photo-interrupter drive circuit -   514 First and second frames photo-reflector drive circuit -   515 Third frame photo-interrupter drive circuit -   516 Fourth frame photo-interrupter drive circuit

BEST MODE FOR CARRYING OUT THE INVENTION

Reference will now be made in detail to the present preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. The scope of the present invention, however, is not limited to these embodiments. Within the scope of the present invention, any structure and material described below can be appropriately modified.

FIGS. 1 to 16B and 20 illustrate a first embodiment of a lens barrel according to the present invention.

In FIGS. 1 to 16B and 20, the lens barrel includes a fixed frame 21 having a fixed cylinder 21 a, a telescopic cylinder unit or telescopic cylinder attached to the fixed frame 21, and a plurality of lens groups disposed in the telescopic cylinder. The telescopic cylinder is movable and collapsible along an optical axis X of the plurality of lens groups.

The lens groups comprise, for example, a first lens group 11, a second lens group 12, a third lens group 13, and a fourth lens group 14, which are disposed in the telescopic cylinder (see FIG. 9).

The telescopic cylinder includes, for example, a first rotary cylinder 22, a first liner 23, a second rotary cylinder 24, a second liner 25, a cam cylinder 26, a lineally-moving cylinder 27, and a third frame 31 (see FIGS. 5 and 8) for retaining the third lens group 13. As described below, the first rotary cylinder 22 and so on are moved along the optical axis with respect to each other with the plurality of lens groups 11 to 14.

As shown in FIG. 9, the first, second, third, and fourth lens groups 11, 12, 13, and 14 are positioned from a subject (not shown) in sequence and disposed on the optical axis X. A shutter/aperture stop unit 15 is disposed between the second lens group 12 and the third lens group 13. The first, second, third, and fourth lens groups 11, 12, 13, and 14, and the shutter/aperture stop unit 15 are configured to be movable in a direction of the optical axis when the telescopic cylinder is moved along the optical direction.

To use the lens barrel for image forming apparatuses or optical devices such as digital cameras or the like, as described hereinafter, for example, a solid-state image-sensing device 16 comprising a CCD (Charge-Coupled Device) or the like is disposed adjacent to the side of an image forming plane of the fourth lens group 14.

Referring to FIG. 9, the first lens group 11 is attached to a first frame 17, and a cover glass 18 and a low-pass filter 19 are disposed adjacent to an image-receiving surface of the CCD 16, if needed.

Generally, as shown in FIG. 9, the lens barrel is structured such that the first to fourth lens groups are movable between a collapsed position S stored in the fixed cylinder 21 a and an extended position D extended out of the fixed cylinder 21 a so as to achieve a zooming, and at least one lens group of the first to fourth lens groups can be retracted out of the optical axis into a retracted position as shown at R in FIG. 9. In the embodiment, at least one portion of the third lens group 13 is retracted from the optical axis passing through a through hole provided in the fixed cylinder 21 a into a stored part provided in the fixed cylinder 21 a and corresponding to the retracted position as described above.

Note that any shape or structure may be used instead of the fixed cylinder. For example, a plurality of peripherally spaced slidable bars or bands may be used without being limited to the cylinder shape of the fixed cylinder.

In regard to this, a further detailed description will be described hereinafter.

The first lens group 11 to the fourth lens group 14 have a zoom lens function in which a focal distance is variable, as described hereinafter. The first lens group 11 includes one or more lens, and is fixed to the lineally-moving cylinder 27 via the first frame 17, which retains the first lens group 11 integrally.

The second lens group 12 includes one or more lens. A cam follower formed on a second frame (not shown) for integrally retaining the second lens group 12 is inserted into a cam groove for the second lens group 12 formed on the cam cylinder 26 shown in FIGS. 9 and 11, and engages with a linear groove 25 a of the second liner 25, and the second lens group 12 is supported by the cam cylinder 26 and the second liner 25.

The shutter/aperture unit 15 includes a shutter and an aperture, and a cam follower formed integrally with the shutter/aperture unit 15 is inserted into a cam groove for the shutter/aperture of the cam cylinder 26 shown in FIG. 11 and is engaged with the linear groove 25 a on the second liner 25 so that the shutter/aperture unit is supported by the cam cylinder 26 and the second liner 25.

The fixed frame 21 includes a cylindrical part having an inner surface which is formed with a linear groove and a helicoidal cam groove along an axial direction, as shown in FIGS. 13A and 13B. A helicoidal cam follower formed on an outer peripheral surface of a base portion of the first rotary cylinder 22 engages with the helicoidal cam groove, as shown in FIG. 13C, and a key portion formed on an inner surface of a base portion of the first liner 23 engages with the linear groove of the fixed frame of the fixed frame 21. An inner surface of the first rotary cylinder 22 is formed with a guide groove extending along a plane transverse to the optical axis X. Engaged with the guide groove is a follower or key which is formed to project from the outer peripheral surface of the first liner 23 in the vicinity of the base portion thereof and acts as a linear member.

An inner surface of the first liner 23 is formed with a linear groove along the optical axis. The first liner 23 is also formed with a clearance groove in which a cam follower formed to project from an outer peripheral surface of a base portion of the second rotary cylinder 24 in the vicinity of the base portion is inserted.

A helicoid is formed on the outer peripheral surface of the base portion of the second rotary cylinder 24, and is engaged with the helicoid of the first liner 23. A cam follower formed to project from the outer peripheral surface of the second rotary cylinder 24 in the vicinity of the base portion engages with the linear groove formed in the inner periphery of the first rotary cylinder 22 through the clearance groove of the cam follower on the first liner 23. A key portion formed to project from the outer peripheral surface of the base portion of the second liner 25 engages with the linear groove provided on the inner peripheral surface of the first liner 23.

An inner surface of the second rotary cylinder 24 is provided with a guide groove along a plane transverse to the optical axis X, a follower or key provided to project from the outer peripheral surface of the second liner 25 is engaged in the guide groove of the second rotary cylinder 24. With such a structure, the second liner 25 moves with the second rotary cylinder 24 in the movement along the optical axis X, while the second rotary cylinder 24 is rotatable relative to the second liner 25.

The cam cylinder 26 fitted to the inner periphery of the second liner 25 is configured in such a manner that an engaging projection formed on the outer peripheral surface of the base portion is fitted to and engaged with the base portion of the second rotary cylinder 24 so as to rotate integrally with the second rotary cylinder 24. The inner surface of the second liner 25 is provided with a guide groove along a surface transverse to the optical axis X, and a follower or key provided on the outer peripheral surface (front side) of the cam cylinder 26 engages with the cam groove. With such a structure, the cam cylinder 26 moves with the second liner 25 in the movement along the optical axis X, while is rotatable relative to the second liner 25.

The base portion of the lineally-moving cylinder 27 is inserted between the second rotary cylinder 24 and the second liner 25, and a cam follower is formed to project from the outer peripheral surface of the lineally-moving cylinder 27 in the vicinity of the base portion, and the cam follower engages with the cam groove formed in the inner peripheral surface of the second rotary cylinder 24. A linear groove is formed on the inner peripheral surface of the lineally-moving cylinder 27 along the axial direction, and the key portion formed on the outer peripheral surface of the second liner 25 engages with the linear groove.

A gear portion is formed on the outer periphery of the base portion of the first rotary cylinder 22, the gear portion is engaged with one or more gears which are driven by a zooming motor 51 so that a drive force of the zooming motor 51 is transmitted to the gear portion via the gears, whereby the first lens group 11, the second lens group 12, and the shutter/aperture unit 15 are zoomed in a predetermined manner. The zooming motor 51 comprises a usual DC motor in the embodiment although it is not limited thereto.

Meanwhile, the cam groove on the second rotary cylinder 24 engaging with the cam follower on the linearly-moving cylinder 27 is shown in FIG. 10.

The cam groove on the cam cylinder 26 which engages with the cam follower on the lens retaining frame of the second lens group 12 and the cam groove of the cam cylinder 26 which engages with the cam follower of the shutter/aperture unit 15 are shown in FIG. 11, respectively.

The cam groove on the first liner 23 which engages with the cam follower of the second rotary cylinder 24 and the straight groove on the first liner 23 which engages with the key groove on the second liner 25 are shown in FIG. 12, respectively.

A linear groove on the fixed frame 21 engaging with the key portion of the first liner 23 of the fixed frame and the cam groove of the fixed frame 21 engaging with the cam follower of the first rotary cylinder 22 are shown in FIGS. 13A to 13C, respectively.

Generally, the rotary cylinder, which is the closest position to the fixed frame and positioned on the outermost circumference is generally screwed onto the fixed frame through a helicoid, and the helicoid is configured to move the rotary cylinder at a constant speed relative to the fixed frame. Therefore, the rotary cylinder is in a half-extended state out of the fixed frame in a short focal length/wide angle in a course in which the rotary cylinder is moved gradually from the collapsed position through the short focal length/wide angle position to a long-focus/telephoto position.

On the contrary, in the structure described above, the first rotary cylinder 22 adjacent to the fixed frame 21 is threaded with the fixed frame of the fixed frame 21 via the cam groove of the helicoidal shape without a simple helicoidal connection. The first rotary cylinder 22 is moved completely to the maximally extended position by being driven from the collapsed position to the short focal length/wide angle position. Thereafter, as shown in FIGS. 13A to 13C, because the subject side end of the cam groove lies in parallel with the end surface of the fixed frame, the first rotary cylinder 22 rotates at a constant position without moving along the optical axis X during driving from the short focal length/wide angle position to the long-focus/telephoto position.

In addition, the third lens group 13 is retracted out of the optical axis X in the collapsed position, in which the lens groups are collapsed in the fixed frame 21, as shown in FIG. 9. The third lens group 13 is moved onto the optical axis X in an extended position of the lens groups.

As the first rotary cylinder 22 is moved from the collapsed position to short focal length/wide angle position, it is extended toward the subject, while rotating in an early stage of the extending out action and when it reach the maximally extended position, a zoom position-detector which is provided on the fixed frame 21 and comprising a photo-reflector, photo-interrupter, leaf switch or the like, for example, generates a zoom position-reference signal. Therefore, when the zoom position-reference signal generates, because it may be determined that the first rotary cylinder 22 reaches the maximally extended position, it is possible to initiate to move the third frame 31 (retractable lens retaining frame according to the present embodiment) onto the optical axis X.

Consequently, a space between the second lens group 12 and the fourth lens group 14 to insert the third lens group 13 into the optical axis X can be secured previously by completely extending out the first rotary cylinder 22 and the first liner 23 adjacent to the fixed frame at the earlier step of the extended action.

As described below, as soon as the first rotary cylinder 22 reaches the maximally extended position, the zoom position-reference signal generates, the space for inserting the third lens group is secured, and immediately, the insertion of the third lens group is initiated. Therefore, a time taking to transit from the collapsed state when an electric source is turned on to the short focal length/wide angle state can be much shortened.

As described above, the retractable third lens group 13 is retained to the third frame 31 (retractable lens retaining frame according to the present embodiment). The third frame 31 retains the third lens group 13 (lens group of the retractable lens retaining frame) at one end thereof, and the other end of the third frame 31 is supported by a third group main-guide shaft 32 which extends substantially in parallel with the optical axis of the third lens group 13 so as to be capable of rotating, and sliding along the third group main-guide shaft 32. The third frame 31 is rotatable about the third group main-guide shaft 32 between a setting position (on-optical-axis position or a photographable position) in which the third lens group 13 is disposed onto the optical axis in a photographing state, as shown in FIG. 8 and the retracted position (collapsed position) in which the third lens group 13 is retracted out of the telescopic cylinder (retracted state) (alternatively, retracted out of the fixed cylinder 21 a into the fixed frame 21), as shown in FIG. 2.

In the vicinity of the third lens group 13 on the side of the rotating end of the third frame 31, a crank-shaped bent portion for differentiating the position of the third lens group 13 in the direction parallel with the main guide shaft between the side of the rotation axis and the side of the supporting portion, a stopper 31 a (FIGS. 15A and 15B) and a light-shielding member 31 b are provided on the rotating end to project from the bent portion substantially toward the rotating end.

The light-shielding member 31 b is configured to be detected by a third-frame photo-interrupter 38 when the third frame 31 is in the retracted position. Thereby, it is possible to detect that the third lens group 13 (the retractable lens retaining frame according to the present embodiment) is in the retracted state.

On the optical performance, in order to lengthen a focus length in the telephoto state, a position of the third lens group 13 in the telephoto state is in an extended position closer to the subject. However, a possible moving amount of the third frame 31 is determined by limitation of a length of the lens barrel in the collapsed state along the optical axis X. It is possible to maximize the focus length in the telephoto state by setting a position for retaining the third lens group by the third frame 31 in the closest position to the subject. However, if a position of the stopper 31 a along the optical axis sets on the generally same position as the third lens group 13, a length of a third frame sub-guide shaft 33 is longer and a size of the lens barrel in the collapsed state becomes greater. Therefore, it is required that the stopper 31 a is set on a side of a focusing position and the third frame 31 is formed into a shape having the crank-shaped bent portion.

Meanwhile, the third frame 31 may be formed from two parts and in this case, one is a member having the crank-shaped bent portion, and the other is a member for retaining the third lens group 13. The two parts operates integrally by being fixed together.

As shown in FIGS. 14A and 14B, a third frame female screw member 35 screwed on a third group lead screw 34 is positioned in the closest position to an image plane of the CCD in the retracted state in which the third frame 31 is retracted. In this state, as shown in FIGS. 15A and 15B, a compression torsion spring 37 is charged or compressed fully so as to impart constantly a clockwise moment M1 (a direction entering toward the optical axis, see FIG. 15A) to the third frame 31 as viewed from the front of the lens barrel, and also so as to press the third frame 31 toward a retainer plate 81.

A cylindrical outer peripheral surface of a supported part provided on the main-guide shaft 32 for the third frame 31 is provided with a stepped portion 31 c, and a cam portion 31 e (cam groove) disposed inside the stepped portion 31 c and formed from an inclined surface, as shown in FIG. 14A.

From this state, when a third frame drive motor 52 is rotated clockwise as viewed from the front of the lens barrel, the third group lead screw 34 is rotated clockwise through a gear mechanism including gears 71 to 74, and the third frame female screw member 35 moves toward the subject along the optical axis X. At this time, the third frame 31 is rotated clockwise by the moment force M1 of the compression torsion spring 37, and the cam portion 31 e engages with a protruded abutting portion (contact portion) 35 c provided on the third frame female screw member 35. Because of the twisting force of the compression torsion spring 37, the cam portion 31 e constantly contacts with the abutting portion 35 c of the third frame female screw member 35. In other words, one end of the compression torsion spring 37 is supported by the fixed frame 21 and the other end of the compression torsion spring 37 contacts with a protrusion 31 h of the third frame 31 to bias the third frame 31, and thereby, the cam portion 31 e constantly contacts with the abutting portion 35 c of the third frame female screw member 35.

As shown in FIGS. 33A and 33B, a part of the cam portion 31 e near to the gear 74 is slanted and a part of the cam portion 31 e facing toward a side of the subject is formed to be perpendicular to the lead screw 34. The third frame 31 is in the retracted state when the abutting portion 35 c is located at a position closest to the gear 74. When the abutting portion 35 c draws away from the gear 74, the slanted part of the cam portion 31 e is supported by the abutting portion 35 c and the third frame 31 starts to rotate by the twisting force of the compression torsion spring 37. The third frame 31 is located in the photographable state when the abutting portion 35 c enters into an inner portion (back portion) 31 g of the cam portion 31 e, and thereby the optical axis of the third lens group 13 of the third frame 31 coincides with other optical axes of the first lens group 11, the second lens group 12 and the fourth lens group 14. When the lead screw 34 is further rotated, the abutting portion 35 c pushes a front engaging portion 31 d of the cam portion 31 e toward the subject so that the third frame 31 moves toward the subject.

Thereafter, when the third frame female screw member 35 is moved in the closest position to the subject by the rotation of the lead screw 34, the light-shielding member 31 b of the third frame 31 is moved to a position out of the third frame photo-interrupter 38 as a device for detecting a position of the third lens group 13 (third lens group position detecting device), thereby the third frame photo-interrupter 38 generates a reference signal in a range from L (or a low) level to H (or a high) level. Accordingly, a position of the third lens group 13 is controlled by pulse count based on the reference signal from the third frame photo-interrupter 38.

From this state, when the third frame female screw member 35 is moved to a retract-initiating position B of the third frame 31, as shown in FIG. 14A, the third frame 31 further rotates clockwise, and the stopper 31 a comes into abutment with the third frame sub-guide shaft 33 as shown in FIGS. 8 and 16A. As a result, a position of the third frame 31 on the optical axis (the on-optical-axis position) is determined. Consequently, approach operation of the third lens group 13 to the optical axis is completed. In the retract-initiating position B, the third frame 31 is movable toward the retracted position S.

Meanwhile, the light-shielding member 31 b shields the third frame photo-interrupter 38 shown in FIG. 16A so that it is possible to detect and confirm that the third frame 31 is in the retracted position S or the retract-initiating position B. When the third frame female screw member 35 is moved to the retract-initiating position B shown in FIG. 14A, the abutting portion 35 c of the third frame female screw member 35 contacts with the front engaging portion 31 d of the stepped portion 31 c of the third frame 31. Again, the stepped portion 31 c of the third frame 31 has the cam portion 31 e which forms a slanted shape on a base end side and the front engaging portion 31 d which forms a planner surface generally perpendicular to the third group main guide shaft 32 on a front end side thereof.

The third frame 31 is constantly biased to move to a direction transverse to the optical axis, i.e., from the retracted position to the optical axis (or to the on-optical-axis position) as well as to a direction along the optical axis, i.e., from the subject to a retainer plate 81 beside the image plane by the compression torsion spring 37 provided on the third group main-guide shaft 32.

The third frame female screw member 35 is formed with a T-shaped protruded member 350 as a portion to be detected (detected portion) at an opposite side of a rotation-preventing projection 35 b which slides in a guide groove G1 as shown in FIG. 15A. The T-shaped protruded member 350 has a substantially alphabet “T” configuration. A vertical line portion located at the center of the alphabet “T” configuration of the T-shaped protruded member 350 is attached to the third frame female screw member 35, whereas a horizontal line portion of the alphabet “T” configuration thereof extends in directions to which the third frame female screw member 35 moves (i.e. an axial direction of the lead screw 34).

The T-shaped protruded member 350 and a transmissive photo-interrupter 351 structure a position detector. The position detector is configured to detect the retracted position in the retracted state of the third frame 31, a position of the third frame 31 on the optical axis X at the time when the entering of the third frame 31 from the retracted position onto the optical axis X has completed in the transition from the retracted state to the photographable state (hereinafter simply referred to as an optical axis entrance completed position), and a distance from a reference position of the third frame 31 or a position of the third frame 31 in the photographable state wherein the focal distance during the wide-angle photographing and the telephoto photographing is changed. Here, an output of the photo-interrupter 351 is outputted to a controller such as a central calculation processing device 501 which will be described later, and the power of the photo-interrupter 351 is supplied from a power source of the camera.

The photo-interrupter 351 is installed near a position within an area that the horizontal line portion of the T-shaped protruded member 350 moves and where the third frame female screw member 35 stands by in a part near to the gear 74 of the lead screw 34 as a home position. The photo-interrupter 351 is installed such that the photo-interrupter 351 once outputs an output of an H level, then outputs an output of an L level, and then outputs the H level output again thereafter, when the third frame female screw member 35 moves from the home position toward the axial direction of the lead screw 34, or when the third frame female screw member 35 returns to the stand by position as the home position from a position distant from the home position.

As shown in FIG. 34, the photo-interrupter 351 outputs the L-level output when the T-shaped protruded member 350 enters between a light-emitting device and a light-receiving device of the photo-interrupter 351 and thus the T-shaped protruded member 350 shields therebetween. The photo-interrupter 351 outputs the H-level output when the T-shaped protruded member 350 does not exist between the light-emitting device and the light-receiving device of the photo-interrupter 351 and thus the light-receiving device receives the light.

More specifically, the position where the photo-interrupter 351 is located is so set that the T-shaped protruded member 350 of the third frame female screw member 35 is out from the photo-interrupter 351 when the T-shaped protruded member 350 is positioned nearest to the gear 74 and thus the H-level output is outputted. Such a location of the installed position of the photo-interrupter 351 is for the purpose of changing the output of the photo-interrupter 351 from “H” to “L” to “H” at the time that the third frame female screw member 35 passes through the photo-interrupter 351 when the third frame female screw member 35 moves from the telephoto to the gear 74 toward the gear 74 to approach utmost to the gear 74, so as to detect that the third frame female screw member 35 has passed though the photo interrupter 351 (or passed between the light-emitting device and the light-receiving device).

The home position of the third frame female screw member 35 is a position where a predetermined time has elapsed from a falling edge of the L-level output (after the predetermined number of pulses is counted) when the third frame female screw member 35 moves from the position nearest to the gear 74 toward the subject side and thus the output of the photo-interrupter 351 changes from “H” to “L” to “H”, as shown in FIG. 34. Such a position where the predetermined amount of time has elapsed from the falling edge of the L-level output is defined as a reference position of the home position.

Thereby, it is possible to determine reference positions for judging an amount of movement of the third frame female screw member 35, and hence it is possible to detect that the third frame 31 is in the state of being positioned at the retracted position. In addition, similarly, it is possible to detect that the third frame 31 is at the optical axis entrance completed position based on elapsing of a predetermined amount of time from a rising edge of the output (before the predetermined number of pulses is counted) when the output of the photo-interrupter 351 rises from the “L” to “H” (a reference position of the optical axis entrance completed position).

Because the reference position for the home position and the optical axis entrance completed position are revealed accurately, it is possible to judge a wide angle photographing position and a telephoto photographing position accurately according to, for example but not limited to, multiplication of the number of rotations and a feeding pitch of the lead screw 34 from the reference position.

More specifically, although the photo-interrupter 351 is shielded by the horizontal line portion of the T-shaped protruded member 350 of the third frame female screw member 35, it is uncertain which part of the horizontal line portion of the T-shaped protruded member 350 is positioned between the light-emitting device and the light-receiving device of the photo-interrupter 351 when the output of the photo-interrupter 351 is the “L” level, since the horizontal line portion of the T-shaped protruded member 350 itself has a certain length in the moving direction thereof. Also, even if the photo-interrupter 351 is able to specify a point of time that the output of the photo-interrupter 351 falls from the “H” to “L”, or a point of time that the output rises from the “L” to “H”, it is difficult to grasp an accurate position of the third frame 31 due to inertia of the motor, the gear mechanism and so on, or a variation in precision of the mechanism for example.

Therefore, a position of the third frame 31, where the third frame 31 is located before a predetermined time elapses from the time when the output of the photo-interrupter 351 has fallen from “H” to “L” and risen from the “L” to “H” again, when the third frame 31 returns to the home position from the position distant from the home position, is defined as the home position. In other words, the home position is the point of time that the output falls from the “H” to “L” and the predetermined time has elapsed therefrom when the third frame female screw member 35 moves from the stand by position toward the subject side.

Accordingly, when the third frame female screw member 35 moves from the stand by state position toward the subject side again and thus the output of the photo-interrupter 351 changes from the “H” to “L” to “H”, it is possible to detect that the third frame female screw member 35 has passed the home position by the detection of the predetermined number of pulses from the falling edge of the “L” level output signal. The predetermined number of pulses from the falling edge of the “L” level output signal to the detection of the predetermined number of pulses is for example determined by measurement of the focal positions of the actual lens barrel or by calculation.

FIG. 35 shows the alternative detected portion. Here, the detected portion detected by the photo-interrupter 351 is an L-shaped protruded member 352 having a substantially alphabet “L” configuration. As similar to the case of the T-shaped protruded member 350 shown in FIG. 34, the installed position of the photo-interrupter 351 is so located that the L-shaped protruded member 352 of the third frame female screw member 35 is out of the photo-interrupter 351 when the L-shaped protruded member 352 is positioned nearest to the gear 74 and thus the H-level output is outputted.

Such a location of the installed position of the photo-interrupter 351 is for the purpose of changing the output of the photo-interrupter 351 from the “H” to “L” to “H” by making the third frame female screw member 35 to pass through the photo-interrupter 351 when the third frame female screw member 35 moves from the telephoto toward the gear 74 to approach utmost to the gear 74, so as to detect that the third frame female screw member 35 has passed though the photo interrupter 351 (or passed between the light-emitting device and the light-receiving device).

Thereby, it is possible to judge that the third frame 31 is in the state of being positioned at the retracted position. Also, it is possible to judge that the third frame 31 is at the optical axis entrance completed position. Additionally, because the reference positions for the home position and the optical axis entrance completed position are judged accurately, it is possible to determine the wide angle photographing position and the telephoto photographing position accurately according to, for example but not limited to, the multiplication of the number of rotations and the feeding pitch of the lead screw from the reference position.

Since operation of the L-shaped protruded member 352 of the third frame female screw member 35 is similar to that of the T-shaped protruded member 350 and the definition of the home position of the third frame female screw member 35 utilizing the rising edge and the falling edge of the output from the photo-interrupter 351 is similar as well, they are not described in detail.

Here, it is to be noted that the configuration of the detected portion of the third frame female screw member 35 detected by the photo-interrupter 351 is not limited to the alphabet “T” or “L” configuration. Other configuration or shape may be employed as long as similar effect described above is obtained by such a shape or configuration.

In addition, a portion of the fixed frame 21 to which the compression torsion spring 37 contacts includes a step 37 a which is formed as a concave portion for inserting one end of the compression torsion spring 37 as shown in FIG. 14B, to prevent the compression torsion spring 37 from deviating out of a center of the third group main-guide shaft 32 considerably.

Next, when the third frame female screw member 35 is moved to a short focal length/wide angle position (the wide angle position W shown in FIG. 14A), because the abutting portion 35 c of the third frame female screw member 35 presses the front engaging portion 31 d, the third frame 31 is movable to the wide angle position along the optical axis X toward the subject.

Moreover, while the third frame female screw member 35 is disposed between the retract-initiating position B and the telephoto position T as shown in FIG. 14A, because the third frame 31 is constantly pressed along the optical axis toward the image plane by the compression torsion spring 37, all spaces generated among the third group lead screw 34, the third frame female screw member 35 and the retainer plate 81 are directed to the image plane, so that the third frame 31 can secure a positional accuracy in the direction of the optical axis.

The third frame female screw member 35 is screwed on the third group lead screw 34 disposed substantially in parallel with the optical axis. The third frame female screw member 35 includes the rotation-preventing projection 35 b in addition to the abutting portion 35 c, which engages with the above-described front engaging portion 31 d or the cam portion 31 e of the third frame 31.

The rotation-preventing projection 35 b is fitted slidably into the guide groove G1 (see FIG. 15A) formed on the cylindrical part of the fixed frame 21 in parallel with the optical axis as a rotation-preventing device for preventing the third frame female screw member 35 from rotating along with the rotation of the third lead screw 34, as shown in FIGS. 15A and 15B. In other words, the third frame female screw member 35 is moved in the back and forth directions along the optical axis by the rotation of the third lead screw 34, because the third frame female screw member 35 is prevented from rotating by the rotation-preventing projection 35 b fitting into the guide groove G1 of the fixed frame 21.

As shown in FIG. 14A in detail, when the third frame female screw member 35 is moved further toward the image plane (left side in the drawing) from the retract-initiating position B shown in FIG. 14A, the third frame female screw member 35 engages with the cam portion 31 e of the stepped portion 31 c of the third lens group-retaining frame 31. The third frame 31 comes into contact with the retainer plate 81 by the biasing force of the compression torsion spring 37 toward the optical axis X direction, and the third frame 31 is rotated counterclockwise against the clockwise biasing force exerted by the compression torsion spring 37. Therefore, it is possible to retract the third frame 31.

On the other hand, while the third frame female screw member 35 is moved from the telephoto position T through the wide angle position W to the retract-initiating position B by the reverse rotation or counterclockwise rotation of the third group lead screw 34, because the abutting portion 35 c of the third frame female screw member 35 engages with the front engaging portion 31 d of the stepped portion 31 c of the third frame 31, the third frame 31 moves gradually to direct from the subject to the image plane while maintaining the position on the optical axis (on-optical-axis position) restricted by the third frame sub-guide shaft 33 by the biasing force toward the optical axis and the biasing force toward the image plane.

Meanwhile, when the third frame female screw member 35 reaches the retract-initiating position B, a base end surface 31 f contacts with the retainer plate 81, and the third frame female screw member 35 is disposed with an interval from the front engaging portion 31 d, and contacts with the cam portion 31 e of the stepped portion 31 c.

While the third frame female screw member 35 moves from the retract-initiating position B to the collapsed position S, the abutting portion 35 c of the third frame female screw member 35 comes into sliding contact with the cam portion 31 e of the stepped portion 31 c of the third frame 31 and rotates the third frame 31 against the rotational biasing force exerted by the compression torsion spring 37, whereby the third frame 31 moves from the position on the optical axis to the collapsed position S. The collapsed position S of the third frame 31 corresponds to a position at which it is moved toward the image plane by a predetermined pulse count number after the generation of the reference signal of the range from the H to the L generated from the third frame photo-interrupter 38. After the third frame 31 is moved to the collapsed position S, the first lens group 11, the second lens group 12, and the shutter/aperture unit 15 are moved to the collapsed position.

In this example, before the third frame 31 is moved to the collapsed position S, a fourth frame 41 for retaining the fourth lens group 14 is first moved to the collapsed position. A first collapsed position of the fourth frame 41 corresponds to a position at which it is moved toward the image plane by a predetermined pulse count number after the generation of a storage reference signal of a range from the H to the L generated by a fourth group reference detector (fourth group photo-interrupter 47). After the fourth frame 41 reaches the first collapsed position, the stored operation of the third frame 31 is initiated.

That is to say, the third frame female screw member 35 moves toward the image plane by a predetermined pulse count number from the generation of the stored reference signal from the H to the L by the third frame photo-interrupter 38 (see FIG. 16A), and the stored operation of the third frame 31 completes. After the completion of the stored operation of the third frame 31, the first rotary cylinder 22 and structural parts disposed inside the first rotary cylinder 22 and the first liner 23 and so on are stored before contacting with the third frame 31. This results in the storage of the first rotary cylinder 22 and so on without interfering with the third frame 31.

Positions of the first rotary cylinder 22 and so on can be set by a drive pulse count generated by a zoom count detector comprising a pinion gear attached directly to an output shaft of the zooming motor 51 and having an encoder structure and a first and second frames photo-interrupter 51 a disposed adjacent the pinion gear, for example.

Meanwhile, although the DC motor is used as the drive source for moving the first rotary cylinder 22 and the drive position of the first rotary cylinder 22 is detected by the detector comprising the encoder and the photo-interrupter, in the above-mentioned example, the similar function can be accomplished by substituting a pulse motor structure for the whole of the above-mentioned structure.

To prevent the third frame 31 from collision with the other parts, an impact-preventing member 36 is, as shown in particular in FIGS. 2 and 7, rotatably supported on the fixed frame 21 in the vicinity of the third group main-guide shaft 32, and includes a rotated portion provided at one end of the impact-preventing member 36 and an engaging projection 36 a. The impact-preventing member 36 is constantly biased to cause the engaging projection 36 a to move toward the optical axis X by a spring or the like.

When the third frame 31 is positioned in the collapsed position, the impact-preventing member 36 is pushed out by rotating force of the third frame 31 against biasing force of the spring, and is deviated outside the third frame 31 (see particularly FIG. 2 and FIG. 7).

When the third frame 31 is rotated and positioned on the optical axis (on-optical-axis position), the impact-preventing member 36 is released from engagement with the third frame 31, and is rotated to cause the engaging projection 36 a to be projected toward the optical axis X by the biasing force, thereby causing the engaging projection 36 a to project from the inner surface of the fixed cylinder 21 a of the fixed frame 21. At this time, in addition to the first rotary cylinder 22 and the first liner 23, the second rotary cylinder 24, the second liner 25, the cam cylinder 26 and the lineally-moving cylinder 27 are all positioned on the subject side with respect to the projected position of the engaging projection 36 a. Therefore, the engaging projection 36 a is positioned to project inwardly of an outer peripheral edge of the base portion of each of the first rotary cylinder 22 and the first liner 23 (see particularly FIG. 5, FIG. 6, and FIG. 8).

With such a structure, even if an operator tries to manually rotate the first rotary cylinder 22 forcibly so as to move it to the collapsed position, the impact-preventing member 36 first contacts with the first rotary cylinder 22. Therefore, because the base portion of the first rotary cylinder 22 cannot be moved toward the image plane than the position of the impact-preventing member 36 along the optical axis, the first rotary cylinder 22 is prevented from contacting with the third frame 31. Accordingly, it is possible to accomplish the prevention of breaking, damage or the like of the third frame 31 due to strong external force. Here, the first rotary cylinder 22 can be moved to the collapsed position only after the third frame 31 is moved to the collapsed position correctly.

Therefore, in a state of being used or in the photographing state of the lens barrel, in which the movable cylinders such as the first rotary cylinder 22 and so on are extended, when a great pressure is exerted on a leading end of the lens barrel and so on by a drop of the lens barrel or the like, the engaging projection 36 a of the impact-preventing member 36 engages with the first rotary cylinder 22 and the first liner 23, and hence further retraction of the first rotary cylinder 22 and the first liner 23 (as well as the second rotary cylinder 24, the second liner 25, the cam cylinder 26, and the lineally-moving cylinder 27) toward the third lens group 13 is prevented. Accordingly, the third frame 31 and the third lens group 13 are prevented from being damaged.

The third group lead screw 34 is rotated in forward and reverse directions by a third frame drive motor 52. The rotation of the third frame drive motor 52 is transmitted to the third group lead screw 34 via gears 71, 72, 73, and 74 arranged in sequence.

Next, a drive structure of the fourth lens group 14 is described with reference to FIGS. 7, 8, 20A and 20B. Note that each of the FIGS. 20A and 20B is a perspective view mainly showing a drive system of the fourth lens group 14.

The fourth lens group 14 comprising at least one optical element (for example but not limited to, a lens) is located nearer to the image plane of the CCD than the third frame 31. The position detector structured by the photo-interrupter 351 and the T-shaped protruded member 350 or the L-shaped protruded member 352 generates a signal indicating that the entering of the third frame 31 into the optical axis X has completed when the state of the retractable lens retaining frame has changed from the collapsed state to the photographable state, and thereafter, permits the movement of the fourth lens group 14.

The fourth lens group 14 used as a focusing lens for focusing the lens groups in the illustrated embodiment is retained by the fourth frame 41, as shown in FIGS. 20A and 20B. The fourth frame 41 includes a sleeve portion 41 a in which a fourth frame main-guide shaft 44 disposed in parallel with the optical axis and fixed to a lens barrel base 82 is fitted, and a rotation-preventing portion 41 b in which a fourth frame sub-guide shaft 42 disposed in parallel with the optical axis and fixed to the lens barrel base 82 is fitted, to restrict the rotation of the fourth frame 41. With such a structure, the fourth frame 41 can be moved freely along the fourth frame main-guide shaft 44, i.e. the optical axis. A fourth frame drive motor 53 comprising a stepping motor is used as a drive source for driving the fourth frame 41 in the illustrated embodiment. Provided on an output shaft of the fourth frame drive motor 53 is a fourth frame lead screw 45 which is threaded into a threaded hole provided in a fourth frame female screw member 46.

The fourth frame 41 has an opening for inserting the fourth frame female screw member 46. The opening has an engaging portion 41 c for engaging with the fourth frame female screw member 46 in a perpendicular plane to the optical axis in a side of the image plane. The fourth frame 41 is always engaged with the fourth frame female screw member 46 by allowing the fourth frame 41 to bias toward the subject by a fourth frame spring 43.

The fourth frame female screw member 46 has a radially projected protrusion 46 a. The protrusion 46 a is engaged in a bore 41 d provided in one side of the opening for inserting the fourth frame female screw member 46 of the fourth frame 41 so that the rotation of the fourth frame female screw member 46 is stopped.

In this way, when the fourth frame drive motor 53 which is the stepping motor for example is driven, the fourth frame lead screw 45 rotates, and hence, the fourth frame female screw member 46 is moved in the forward and reverse directions along an axis of the fourth frame lead screw 45 (i.e. the optical axis X). Because the fourth frame 41 engages with the fourth frame female screw member 46, the fourth frame 41 is moved along the optical axis following to the movement of the fourth frame female screw member 46. In this case, although the fourth frame lead screw 45 is formed on the output shaft of the fourth frame drive motor 53, the fourth frame lead screw 45 may be rotated by structuring the fourth frame drive motor 53 and the fourth frame lead screw 45 separately and connecting them through gears or the like.

The fourth frame 41 is provided with a light-shielding piece 41 e which shields an optical passage of a fourth group photo-interrupter 47 provided on the lens barrel base 82. The light-shielding piece 41 e is capable of light-shielding or passing light through the optical passage of the fourth group photo-interrupter 47 in response to the movement of the fourth frame 41. In this case, the fourth frame 41 can be moved in a predetermined position by recognizing as a reference position a time at which the light-shielding pieces is set from the light-shielding state to the light-passing state and energizing a pulse waveform of any pulse number from the reference position to rotate the fourth frame drive motor 53.

Meanwhile, the fourth frame 41 has a concave portion 41 f which is provided in an outer peripheral edge thereof and allows the light-shielding member 31 b of the third frame 31 for the photo-interrupter 38 to move toward the optical axis to avoid the interference with the fourth frame 41, thereby the movement amount of the fourth frame 41 can be increased and a range capable of focusing can be enlarged. Moreover, as described above, there is a clearance between the fourth frame 41 and the fourth frame female screw member 46 in the direction of the optical axis, but the position in the direction of the optical axis of the fourth frame 41 can be controlled accurately by constantly biasing the fourth frame 41 toward the subject by the fourth frame spring 43.

The collapsed position of the first rotary cylinder 22, the first liner 23, the first lens group 11, the second lens group 12, and the shutter/aperture unit 15 is controlled based on the zoom position-reference signal generated by the zoom position detector comprising the photo-reflector and so on disposed in the fixed frame 21. That is to say, it is possible to complete the storing operation by moving them toward the image plane by the predetermined pulse count number of the drive pulse generated by the pinion gear acting as the encoder and the zoom count detector disposed adjacent to the pinion gear after the change of from the H to the L of the zoom position storage reference signal occurs.

In storing, the fourth frame 41 is positioned in the first collapsed position as described above, while, when the first rotary cylinder 22 is moved to the collapsed position, the most distal surface of the first rotary cylinder 22 or the first liner 23 contacts with the fourth frame 41 and presses the fourth frame 41 to move to the second collapsed position finally.

By such an operation, even if variations of the attached position of the fourth group photo-interrupter 47 in the direction of the optical axis occur, the fourth frame 41 can be moved to the collapsed position accurately without requiring a complicated adjustment. Such an operation can be accomplished for the reason that a length of the engaging space formed in the fourth frame 41, in the direction of the optical axis is larger than a thickness of the fourth frame female screw member 46.

The zooming motor 51 for moving the first lens group 11, the second lens group 12, and the shutter/aperture unit 15 is structured by the DC motor for example as described above in the illustrated embodiment. The third frame drive motor 52 for driving the third lens group 13 and the fourth frame drive motor 53 for driving the fourth lens group 14 are generally configured to use a pulse motor for example. The zooming motor 51, the third frame drive motor 52 and the fourth frame drive motor 53 are driven in conjunction with each other in a software-like manner to achieve an appropriate zooming action performed mainly by the first to the third lens groups 11-13 and an appropriate focusing action performed mainly by the fourth lens group 14, for example.

Now, a drive control system for the lens groups structuring the lens barrel is described in detail with reference to FIGS. 21 to 28.

The drive control system is shown in FIG. 21. The drive control system includes the central calculation processing device 501, a motor driver 502, a first and second frames DC motor 503, a first aperture stop motor 504, a second aperture stop motor 505, a shutter motor 506, a third frame pulse motor 507, a fourth frame pulse motor 508, a first and second frames photo-interrupter 509, a first and second frames photo-reflector 510, the third frame photo-interrupter 351 (the third frame photo-interrupter 351 and the T-shaped protruded member 350 or the L-shaped protruded member 352 structure the position detector for the detection of the location of the third frame 31), a fourth frame photo-interrupter 512, a first and second frames photo-interrupter drive circuit 513, a first and second frames photo-reflector drive circuit 514, a third frame photo-interrupter drive circuit 515, and a fourth frame photo-interrupter drive circuit 516.

The central calculation processing device 501 gives a command such as an initial setting of the motor driver 502, the selection for a drive motor, the setting of a drive voltage, a direction for driving and so on, to the motor driver 502. The motor driver 502 controls the motor system of the first and second frames DC motor 503, the first aperture stop motor 504, the second aperture stop motor 505, the shutter motor 506, the third frame pulse motor 507, the fourth frame pulse motor 508 and so on, in accordance with the command from the central calculation processing device 501.

The first and second frames DC motor 503 drives the first and second lens groups 11 and 12. As always, the first and second groups 11 and 12 are driven separately with respect to each other through a cam mechanism in response to the drive of the first and second frames DC motor 503. The first aperture stop motor 504 and the second aperture stop motor 505 are configured to drive an aperture stop of the shutter/aperture unit 15. The shutter motor 506 drives a shutter of the shutter/aperture unit 15. The third frame pulse motor 507 drives the third lens group 13. The fourth frame pulse motor 508 drives the fourth lens group 14.

The central calculation processing device 501 supplies a drive electricity to the first and second frames photo-interrupter 509, the first and second frames photo-reflector 510, the third frame photo-interrupter 351 (structures the position detector with the T-shaped protruded member 350 or the L-shaped protruded member 352), and the fourth frame photo-interrupter 512 as the device for detecting position through the first and second frames photo-interrupter drive circuit 513, the first and second frames photo-reflector drive circuit 514, the third frame photo-interrupter drive circuit 515, and the fourth frame photo-interrupter drive circuit 516. The central calculation processing device 501 also acquires a positional information signal detected by the first and second frames photo-interrupter 509, the first and second frames photo-reflector 510, the third frame photo-interrupter 351, and the fourth frame photo-interrupter 512.

The first and second frames photo-interrupter drive circuit 513, the first and second frames photo-reflector drive circuit 514, the third frame photo-interrupter drive circuit 515, and the fourth frame photo-interrupter drive circuit 516 have a function to control suitably a level of a projecting current and an output signal of each of the first and second frames photo-interrupter 509, the first and second frames photo-reflector 510, the third frame photo-interrupter 351, and the fourth frame photo-interrupter 512.

The motor driver 502 receives a command from the central calculation processing device 501 and executes the command. The central calculation processing device 501 sets a designated voltage to one or more selected motors of the first and second frames DC motor 503, the first aperture stop motor 504, the second aperture stop motor 505, the shutter motor 506, the third frame pulse motor 507, the fourth frame pulse motor 508, and controls them in accordance with a timing of drive command.

Here, a lens barrier 62 for protecting the lens barrel is described as follows.

The lens barrier 62 shown in FIG. 3 to FIG. 5 is disposed to cover a side of the first lens group 11 facing the subject, in the stored state, and protects the lens group from contaminations or damages. The lens barrier 62 is moved in back and forth directions transverse to the optical axis by a barrier drive system 63. FIGS. 3 and 4 show a state in which the lens barrier 62 is closed, and FIG. 5 shows a state in which the lens barrier 62 is almost opened. The barrier drive system 63 drives the lens barrier 62 between the closed position (FIGS. 3 and 4) and the opened position (a position farther from the optical axis than the position shown in FIG. 5) through the operation of a barrier-operating element (see a barrier-operating element 301 in FIG. 17A). The barrier drive system 63 has a function to bias the lens barrier 62 in a closing direction at the closed position and in an opening direction at the opened position.

Therefore, when driving the lens barrier 62 in the closed state toward the opening direction, the lens barrier 62 is moved to the opened state semi-automatically when the lens barrier 62 passes a predetermined position. Also, when an attempt is made to close the lens barrier 62 from the opened state, the lens barrier 62 is moved to the closed state semi-automatically when the lens barrier 62 passes a predetermined position. The position in the closed state is not necessarily required to be the same as the predetermined position in the opened state; rather, it is preferable that the lens barrier has a certain degree of hysteresis characteristics in the movement to accomplish a smooth operation of the lens barrier 62.

A barrier control member 61 is provided on a side of the fixed frame 21 in the direction of opening the lens barrier 62 so as to be capable of sliding in a direction along the optical axis, and is biased toward the subject by a spring or the like as needed. In the stored state, an engaging portion of the barrier control member 61 which is formed into a bent shape engages with base edge surfaces of the first rotary cylinder 22 and the first liner 23 and is biased toward the image surface against biasing force of the spring, and hence is not in contact with the lens barrier 62. In the used or photographing state, the lens barrier 62 is completely away from the respective lens groups and retaining frames thereof. In this state, engagement of the engaging portion of the barrier control member 61 is released, and hence the barrier control member 61 is biased toward the subject by the biasing force, and then, a barrier-intercepting portion at the distal end enters into a passage of the lens barrier 62.

In this state, when the lens barrier 62 is rapidly operated to move the lens barrel to the collapsed position, there is a possibility that the lens barrier 62 hits against the lens barrel. However, since the barrier-intercepting portion at the distal end of the barrier control member 61 crosses the passage of the lens barrier 62, the lens barrier 62 is prevented from entering into a moving passage of the lens barrel. When the respective lens groups are stored and the stored state is completed, the base edge surfaces of the first rotary cylinder 22 and the first liner 23 engage with the engaging portion of the barrier control member 61, which is formed into the bent shape, to energize the engaging portion toward the image surface against the biasing force. Therefore, the lens barrier 62 can be moved to the front portion of the lens barrel, and hence the lens barrier 62 is correctly set to the closed position. In this manner, the interference between the lens barrier 62 and the lens cylinders retaining the lens groups can be effectively prevented.

<Activation Sequence>

An activation sequence of the above-mentioned drive control system is explained with reference to FIG. 22.

By opening the lens barrier 62, a barrier switch signal (barrier SW) from a barrier switch (not shown) changes from the H to the L and an initial setting of the lens barrel is initiated. Meanwhile, the barrier switch is operated by opening mechanically the lens barrier 62 with an operating lever or the like (not shown), while the lens barrier may be opened by operation of the barrier switch. Executing of the initial setting causes the initialization of the motor driver 502 for driving the motor system, and also causes the initialization of the first and second frames photo-interrupter 509, the first and second frames photo-reflector 510, the third frame photo-interrupter 351 (position detector), and the fourth frame photo-interrupter 512, as the position detecting devices which detect positions through the first and second frames photo-interrupter drive circuit 513, the first and second frames photo-reflector drive circuit 514, the third frame photo-interrupter drive circuit 515, and the fourth frame photo-interrupter drive circuit 516.

In the case that detected results by the first and second frames photo-interrupter 509, the third frame photo-interrupter 351, and the fourth frame photo-interrupter 512 indicate the collapsed position, the first and second frames DC motor 503 is adapted to be driven toward the wide angle position. A driven amount of the first and second frames DC motor 503 is detected by the first and second frames photo-interrupter 509 for detecting the moving amount of the first and second lens groups. The moving amount is detected by counting edge portions of the pulse signal (PI signal) by the first and second frames photo-interrupter 509.

During an activation period immediately after the first and second frames DC motor 503 is activated, the drive voltage is set to be lower than a constant voltage so as to prevent a rush current by the DC motor. After the activation period is completed, the drive voltage is increased to a stationary voltage.

A period for monitoring the barrier switch (barrier SW) immediately after the initiation of the activation of the first and second frames DC motor 503 is set and a state of the barrier switch signal is monitored by the central calculation processing device 501. During the monitoring period, if the barrier switch signal indicates the opening state of the lens barrier, the shutter is set in the full opening by the shutter motor 50 for driving the shutter. Then, the aperture stop is set in an intermediately restricted state by the first and second aperture stop motors 504 and 505. In this example, although the aperture stop is set in the intermediately restricted state, the aperture stop may be set in an opened state (fully opened state).

Subsequently, the fourth lens group 14 is previously driven through the fourth pulse motor 508. By achieving the previous drive of the fourth lens group 14, the total time from the initiation of the drive of the first and second lens groups 11 and 12 to the completion of the drive of the final fourth lens group 14 can be reduced. Moreover, it is possible to greaten a torque when driving and thereby to prevent the interference of the fourth lens group 14 with the other parts by setting a pulse rate of the fourth frame pulse motor 508 in the previous drive thereof lately than that in the normal driving state.

Meanwhile, the driven amount of the fourth lens group 14 by the fourth frame pulse motor 508 is set so that the third and fourth lens groups 13 and 14 do not interfere with each other.

When the previous drive of the fourth lens group 14 is completed, the waiting for the reference position detection by the first and second frames photo-reflector 510 is set. A place where the reference position signal (HP signal) changes from the H to the L becomes the reference position (HP position) of the first and second lens groups 11 and 12. When the reference position (HP position) of the first and second lens groups 11 and 12 is detected, positional information of the first and second lens groups 11 and 12 is reset. In this embodiment, the HP position of the first and second lens groups 11 and 12 is configured to be detected by way of detecting the position of first and second frames. The movement of the first and second lens groups 11 and 12 is controlled by counting the pulse-like signal (PI signal) by the first and second frames photo-interrupter 509 so as to acquire the movement amount of the first and second lens groups 11 and 12 based on the positional information to the wide angle position. The wide angle position is previously set, but it can be changed by storing it in a nonvolatile memory such as an EEPROM (Electronically Erasable and Programmable Read Only Memory) or the like and rewriting it.

A specified pulse period before reaching the wide angle position is a stop controlling period, in which the drive voltage is lowered in accordance with residual pulse numbers to the wide angle position so as to reduce overrun in reaching the wide angle position. If the first and second lens groups 11 and 12 reach the wide angle position by counting the PI signal by the first and second frames photo-interrupter 509, a braking control is made in order to stop the first and second lens groups 11 and 12. An amount of overrun during the braking period is also counted to decide the final position of the first and second lens groups 11 and 12.

Moreover, when the reference position (HP position) of the first and second lens groups 11 and 12 is detected, the drive of the third frame pulse motor 507 in the direction of wide angle position is initiated to control the third lens group 13 with the first and second lens groups 11 and 12. The driving time of the third lens group 13 can be reduced by setting the pulse rate in driving the third group pulse motor highly or rapidly than that in the normal drive.

In the third lens group 13, as described above, the retracted position in the retracted state of the third frame 31, the optical axis entrance completed position of the third frame 31 at the time that the state has changed from the retracted state to the photographable state, and the distance from the reference position or the position of the third frame 31 in the photographable state in which the focal distance during the wide-angle photographing and the telephoto photographing is changed, are detected by the position detector structured by the T-shaped protruded member 350 or the L-shaped protruded member 352 and the transmissive photo-interrupter 351. More specifically, the third lens group 13 is waited for detecting the reference position by the third frame photo-interrupter 351. The position at which the predetermined number of pulses from the place where the reference position signal (HP signal) detected by the third frame photo-interrupter 351 has changed from the L to the H is detected becomes the reference position (HP position) of the third lens group 13. When the reference position (HP position) is detected, positional information of the third lens group 13 is reset. In this embodiment, the HP position of the third lens group 13 is configured to be detected by way of detecting the position of the third frame 31. The third lens group 13 is pulse-driven according to the movement amount to the wide angle position by the third frame pulse motor 507 on the basis of the detected position (HP position). The wide angle position is previously set, but it can be changed by storing it in the nonvolatile memory such as the EEPROM or the like and rewriting it.

Alternatively, the third frame photo-interrupter 351 may be configured to determine the reference position (HP position) of the third lens group 13 by defining that the place where the reference position signal (HP signal) detected by the third frame photo-interrupter 351 has changed from the L to the H is the reference position (HP position) of the third lens group 13. As well as in this case, when the reference position (HP position) is detected, the positional information of the third lens group 13 is reset, and then the third lens group 13 is pulse-driven according to the movement amount to the wide angle position by the third frame pulse motor 507 on the basis of the detected position (HP position). The wide angle position is previously set, but it can be changed by storing it in the nonvolatile memory such as the EEPROM or the like and rewriting it.

In addition, the final stopping position of the third lens group 13 is the position in which the overrun of the first and second lens groups 11 and 12 is considered. That is to say, because the stopped position of the first and second lens groups 11 and 12 is “the wide angle position plus the overrun amount” due to the overrun, the stopped position of the third lens group 13 is also “the wide angle position plus “x”” in consideration of the overrun of the first and second lens groups 11 and 12. A value of the “x” is obtained by a linear calculation depending on pulse numbers between the zooming positions of the first and second lens groups 11 and 12, the overrun amount, and a pulse number between the zooming positions of the third lens group 13. The zooming position is one of sections divided into 16 equally between the wide angle position and the telephoto position (between W and T).

The drive of the fourth frame pulse motor 508 in the direction of a wide angle infinite position is initiated when the drive of the first and second lens groups 11 and 12 is completed, the reference position (HP position) of the third lens group 13 is detected, and the third lens group 13 is driven more than the specified pulse number.

If the drive of the first and second lens groups 11 and 12 is not completed, or the third lens group 13 is not driven more than the specified pulse from the reference position, a standby state is set until the drive of the first and second lens groups 11 and 12 is completed as well as the third lens group 13 is driven more than the specified pulse from the reference position.

When the fourth frame pulse motor 508 is driven in the state that the drive of the first and second lens groups 11 and 12 are not completed, the three motors are driven simultaneously and consequently, current consumption increases. Therefore, in such a case, only the third and fourth lens groups 13 and 14 are driven simultaneously. Moreover, when the fourth lens group 14 is driven before the third lens group 13 reaches the position more than the specified pulse number, the interference between the third and fourth lens groups 13 and 14 occurs. Therefore, the drive of the fourth lens group 14 is initiated after the third lens group 13 is driven more than the specified pulse number.

The fourth lens group 14 is waited for detecting the reference position by the fourth frame photo-interrupter 512. In addition, the drive voltage of the fourth frame pulse motor 508 is set to be lower than that of the normal drive so as to reduce the current consumption. A place where the reference position signal (HP signal) by the fourth frame photo-interrupter 512 has changed from the L to the H becomes the reference position (HP position) of the fourth lens group 14. When the reference position (HP position) of the fourth lens group 14 is detected, positional information of the fourth lens group 14 is reset. In this embodiment, the HP position of the fourth lens group 14 is configured to be detected by way of detecting the position of the fourth frame 41. The fourth lens group 14 is pulse-driven according to the detected reference position (HP position) by the fourth frame pulse motor 508 on the basis of the movement amount to the wide angle infinite position. The wide angle infinite position is previously set, but it can be changed by storing it in a nonvolatile memory such as the EEPROM or the like and rewriting it.

FIG. 36 shows a part of a timing chart when the retractable lens retaining frame 31 moves from the retracted position to the photographable position and when the fourth lens group 14 is moved in the optical axis direction to perform the focusing process.

When the lens barrier 62 is opened so as to transit the state to the photographable state, the zoom motor signal is turned from “OFF” to “ON” (time t1 in FIG. 36), and the first rotary cylinder 22 starts to move from the collapsed position (collapsed state) toward the subject (t1). When the first rotary cylinder 22 moves to a front position part on the subject side and approaches the front position part (t2), the zoom position-reference signal changes from L to H, and also the third frame drive motor 52 for driving the retractable lens retaining frame 31 changes from “OFF” to “ON” to start rotating (t3). The retractable lens retaining frame 31 is driven by the movement of the third frame female screw member 35.

Then, the retractable lens group detector reference signal is generated, at the time that the predetermined number of pulses is counted after the output of the photo-interrupter 351 has fallen from “H” to “L”, when the T-shaped protruded member 350 or the L-shaped protruded member 352 goes through the photo-interrupter 351 from the stand by position in the collapsed state and (t4).

In accordance with the change of the retractable lens group motor signal from “OFF” to “ON”, the retractable lens retaining frame 31 is made to coincide the optical axis of own retracted lenses with the optical axis of lenses of other lens groups (i.e., the optical axis X) to place the condition to the photographable state, and then, the retractable lens retaining frame 31 is moved toward the subject. After the zoom position-reference signal has changed from “H” to “L” by the movement of the first rotary cylinder 22 (t5) and the retractable lens retaining frame 31 has moved to the subject side to change the retractable lens group detector reference signal from “H” to “L” (t6), the motor 53 of the fourth lens group 14 starts to rotate in the time (t6) to initiate a focusing process (t6).

The focusing lens detector reference signal of the fourth lens group 14 changes from “L” to “H” (t7), and the motor 53 of the fourth lens group 14 initiates the focusing process, and thereafter, the motor 52 for moving the retractable lens retaining frame 31 is stopped (t8). Then, the motor 53 of the fourth lens group 14 stops after the motor 52 for moving the retractable lens retaining frame 31 is stopped (t9) to end the focusing process.

Thereafter, when the lens barrier 62 is closed for example, the state thus transits from the photographable state to the collapsed state according to a collapsing process. The collapsing process follows a process substantially opposite of the above-described process, which will be described later.

In the embodiment, as described above and shown in the timing chart of FIG. 22, the number of motors driven simultaneously is limited to two so as to reduce the current consumption as well as to shorten the time required for activation by the optimum drive of the motors.

Next, a case in which the barrier switch signal is changed in a closed state during a period for monitoring the barrier switch immediately after the activation of the first and second frames DC motor 503 is initiated is described with reference to FIG. 23. If the barrier switch signal is changed from the opened state to the closed state during the period, the drive of the first and second frames DC motor 503 is stopped.

Thereafter, the drive of the first and second frames DC motor 503 by a movement amount or by the specified pulse number toward the direction of the collapsed position is initiated. In this case, the drive voltage is made lower so as to prevent generation of breaking and damage even if operating parts of the lens barrier hit against the first and second lens groups and so on in the end of the collapsed position. By such a control, the first and second lens groups 11 and 12 are prevented from interfering with the lens barrier.

[Reset Sequence]

Moreover, if the detected result of the first and second photo-reflector 510 is not the collapsed position (reference position HP, signal=L), the detected result of the third frame photo-interrupter 351 is not the collapsed position (reference position HP, signal=H), or the detected result of the fourth frame photo-interrupter 512 is not the collapsed position (reference position HP, signal=H), the reset sequence drive is executed.

The reset sequence is described referring to FIGS. 24A and 24B, wherein FIG. 24A is a table showing the reset sequence of the lens barrel, and FIG. 24B is a timing chart of the HP signals.

<When First and Second Group HP Signal=H, Third Group HP Signal=L, Fourth Group HP Signal=L>

First, as the reset operation of the first and second lens groups 11 and 12, the reference position (HP position) of the first and second lens groups 11 and 12 is detected, and the first and second lens groups 11 and 12 are moved to the wide angle position (first and second groups: Reset). Next, as the storing operation of the fourth lens group 14, the reference position (HP position) of the fourth lens group 14 is detected, and the fourth lens group 14 is moved to the collapsed position (fourth group: Storage).

Subsequently, as the reset operation of the third lens group 13, the reference position (HP position) of the third lens group 13 is detected, and the third lens group 13 is moved to the wide angle position (third group: Reset).

Finally, as the reset operation of the fourth lens group 14, the reference position (HP position) of the fourth lens group 14 is detected, and the fourth lens group 14 is moved to the wide angle infinite position (fourth group: Reset).

<When First and Second Group HP Signal=H, Third Group HP Signal=L, Fourth Group HP Signal=H>

First, as the retiring operation of the first and second lens groups 11 and 12, the first and second lens groups 11 and 12 are driven in the direction of the telephoto and pulse-driven by the specified pulse after the lowering of the reference signal is detected (first and groups; Retire). Next, as the storing operation of the fourth lens group 14, the reference position (HP position) of the fourth lens group 14 is detected, and the fourth lens group 14 is moved to the collapsed position (fourth group: Storage). Subsequently, as the reset operation of the first and second lens groups 11 and 12, the reference position (HP position) of the first and second lens groups 11 and 12 is detected, and the first and second lens groups 11 and 12 are moved to the wide angle position (first and second groups: Reset).

Next, as the reset operation of the third lens group 13, the reference position (HP position) of the third lens group 13 is detected, and the third lens group 13 is moved to the wide angle position (third group: Reset). Finally, as the reset operation of the fourth lens group 14, the reference position (HP position) of the fourth lens group 14 is detected, and the fourth lens group 14 is moved to the wide angle infinite position (fourth group: Reset).

<When First and Second Group HP Signal=H, Third Group HP Signal=H, Fourth Group HP Signal=L>

<When First and Second Group HP Signal=H, Third Group HP Signal=H, Fourth Group HP Signal=H>

First, as the retiring operation of the first and second lens groups 11 and 12, the first and second lens groups 11 and 12 are driven in the direction of the telephoto and pulse-driven by the specified pulse after the lowering of the reference signal is detected (first and groups; Retire). Next, as the storing operation of the fourth lens group 14, the reference position (HP position) of the fourth lens group 14 is detected, and the fourth lens group 14 is moved to the collapsed position (fourth group: Storage). If the reference position (HP position) of the fourth lens group 14 can be detected, the reference position (HP position) of the third lens group 13 is detected and the third lens group 13 is moved to the collapsed position as the storing operation of the third lens group 13 (third group: Storage). If the reference position (HP position) of the fourth lens group 14 cannot be detected, because it is considered that the fourth lens group 14 is interfered with the third lens group 13, the storing operation of the third lens group 13 is previously carried out (third group: Storage).

If the storing operation of the third lens group 13 is completed, the storing operation of the fourth lens group 14 is then carried out (fourth group: Storage). If the HP position is not detected at the time of operating the storage of the third lens group 13, because it is considered that the third lens group 13 is interfered with the fourth lens group 14, the third lens group 13 is driven by the specified pulse count in the direction of the telephoto as the retiring operation of the third lens group 13 (third group: Retire). Thereafter, the storing operation (fourth group: Storage) of the fourth lens group 14 and the storing operation (third group: Storage) of the third lens group 13 are carried out.

Subsequently, as the reset operation of the first and second lens groups 11 and 12, the reference position (HP position) of the first and second lens groups 11 and 12 is detected, and the first and second lens groups 11 and 12 are moved to the wide angle position (first and second groups: Reset). Next, as the reset operation of the third lens group 13, the reference position (HP position) of the third lens group 13 is detected, and the third lens group 13 is moved to the wide angle position (third group: Reset). Finally, as the reset operation of the fourth lens group 14, the reference position (HP position) of the fourth lens group 14 is detected, and the fourth lens group 14 is moved to the wide angle infinite position (fourth group: Reset).

<When First and Second Group HP Signal=L, Third Group HP Signal=L, Fourth Group HP Signal=L>

<When First and Second Group HP Signal=L, Third Group HP Signal=L, Fourth Group HP Signal=H>

First, as the storing operation of the fourth lens group 14, the reference position (HP position) of the fourth lens group 14 is detected, and the fourth lens group 14 is moved to the collapsed position (fourth group: Storage). Next, as the storing operation of the third lens group 13, the reference position (HP position) of the third lens group 13 is detected, and the third lens group 13 is moved to the collapsed position (third group: Storage). Next, as the reset operation of the first and second lens groups 11 and 12, the reference position (HP position) of the first and second lens groups 11 and 12 is detected, and the first and second lens groups 11 and 12 are moved to the wide angle position (first and second groups: Reset). Subsequently, as the reset operation of the third lens group 13, the reference position (HP position) of the third lens group 13 is detected, and the third lens group 13 is moved to the wide angle position (third group: Reset). Finally, as the reset operation of the fourth lens group 14, the reference position (HP position) of the fourth lens group 14 is detected, and the fourth lens group 14 is moved to the wide angle infinite position (fourth group: Reset).

<When First and Second Group HP Signal=L, Third Group HP Signal=H, Fourth Group HP Signal=L>

<When First and Second Group HP Signal=L, Third Group HP Signal=H, Fourth Group HP Signal=H>

First, as the storing operation of the fourth lens group 14, the reference position (HP position) of the fourth lens group 14 is detected, and the fourth lens group 14 is moved to the collapsed position (fourth group: Storage).

If the reference position (HP position) of the fourth lens group 14 can be detected, as the storing operation of the third lens group 13, the reference position (HP position) of the third lens group 13 is detected, and the third lens group 13 is moved to the collapsed position (third group: Storage).

If the reference position (HP position) of the fourth lens group 14 cannot be detected, because it is considered that the fourth lens group 14 is interfered with the third lens group 13, the storing operation of the third lens group 13 is previously carried out (third group: Storage). If the storing operation of the third lens group 13 is completed, the storing operation of the fourth lens group 14 is then carried out (fourth group: Storage).

If the HP position is not detected at the time of operating the storage of the third lens group 13, because it is considered that the third lens group 13 is interfered with the fourth lens group 14, the third lens group 13 is driven by the specified pulse count in the direction of the telephoto as the retiring operation of the third lens group 13 (third group: Retire).

Thereafter, the storing operation (fourth group: Storage) of the fourth lens group 14 and the storing operation (third group: Storage) of the third lens group 13 are carried out.

Subsequently, as the reset operation of the first and second lens groups 11 and 12, the reference position (HP position) of the first and second lens groups 11 and 12 is detected, and the first and second lens groups 11 and 12 are moved to the wide angle position (first and second groups: Reset). Next, as the reset operation of the third lens group 13, the reference position (HP position) of the third lens group 13 is detected, and the third lens group 13 is moved to the wide angle position (third group: Reset). Finally, as the reset operation of the fourth lens group 14, the reference position (HP signal) of the fourth lens group 14 is detected, and the fourth lens group 14 is moved to the wide angle infinite position (fourth group: Reset).

[Storing Sequence]

The barrier switch signal changes from L to H by closing the lens barrier 62 to initiate the storing operation. Meanwhile, the barrier switch may be operated by mechanically closing the lens barrier 62 by means of an operating lever or the like, or the lens barrier 62 may be closed by operation of the barrier switch.

The shutter of the shutter/aperture stop unit 15 is set in the fully closed state through the full closing control of the shutter by the shutter motor 506. Next, the aperture stop of the shutter/aperture stop unit 15 is set in the intermediately restricted state through the intermediate restricting control of the aperture stop by the first and second aperture stop driving motors 504 and 505. Subsequently, the storing drive of the fourth lens group 14 is achieved through the fourth frame pulse motor 508. The standby for detecting the reference position of the fourth frame pulse motor 508 by the fourth frame photo-interrupter 512 is set after the drive of the fourth frame pulse motor 508 to the collapsed position is initiated.

The fourth frame pulse motor 508 is pulse-driven by the movement amount to the collapsed position from the place where the reference positional signal (HP signal) by the fourth frame photo-interrupter 512 changes from H to L. The movement amount to the collapsed position is previously set, but the movement amount can be changed by storing it in the nonvolatile memory such as the EEPROM or the like and rewriting it.

Next, the drive of storing the third lens group 13 is executed through the third frame pulse motor 507. The third lens group 13 is waited for detecting the reference position by the third frame photo-interrupter 351 by initiating the drive of the third frame pulse motor 507 in the direction of the collapsed position.

The third lens group 13 is pulse-driven by the movement from the place where the reference position signal (HP signal) by the third frame photo-interrupter 351 has changed from H to L to the collapsed position. Although the movement amount to the collapsed position is set previously, the movement amount can be changed by storing it in the nonvolatile memory such as the EEPROM or the like and rewriting it.

The drive pulse rate of the third frame pulse motor 507 between the reference position and the collapsed position is lower than the drive pulse rate until the reference position. In this way, a smooth pulse drive can be accomplished by changing the pulse rate in accordance with an area in which a torque is necessary.

Next, the drive of storing the first and second lens groups 11 and 12 is executed through the first and second frames DC motor 503. The first and second lens groups 11 and 12 are waited for detecting the reference position by the first and second frames photo-reflector 510 by initiating the drive of the first and second frames DC motor 503 in the direction of the collapsed position.

The control for the movement amount of the first and second lens groups 11 and 12 is achieved by counting the pulse-like signal (PI signal) by the first and second frames photo-interrupter 509 to acquire the movement amount from the place where the reference position signal (HP signal) by the first and second frames photo-reflector 510 has changed from L to H to the collapsed position. Although the movement amount to the collapsed position is set previously, the movement amount can be configured to be changed by storing it in the nonvolatile memory such as the EEPROM or the like and rewriting it.

In the drive for storing the first and second lens groups 11 and 12, the PI signal is counted by the first and second frames photo-interrupter 509 without dropping the voltage of the first and second frames DC motor 503 before stopping it, and when the first and second lens groups 11 and 12 reach the collapsed position, a breaking control is achieved in order to stop the drive of the first and second lens groups 11 and 12. This is to prevent the first and second group DC motor from stopping at the middle of the drive due to the dropping of voltage.

[Changing Magnification Sequence]

A sequence for operating a changing magnification is described with reference to a flow chart shown in FIG. 26.

When a changing magnification process is initiated by operating a zoom lever, zoom button or the like, whether it is necessary to retire the fourth lens group 14 is determined (step S11). It is determined in the step S11 that the retire process for the fourth lens group 14 is required if the fourth lens group 14 is disposed in a nearer position than a predetermined position in the changing magnification process from the telephoto to the wide angle. Next, a direction of drive of the changing magnification is determined (step S12). If it is the changing magnification from the wide angle to the telephoto, the drive of the first and second lens groups 11 and 12 is initiated by operating the first and second frames DC motor 503 (step S13).

Next, whether the first and second lens groups 11 and 12 are to be stopped is determined (step S14). It is determined in the step S14 that the first and second lens groups 11 and 12 are stopped in a case satisfying one of conditions in which: if a zoom driving switch operated by changing magnification manipulation through the zoom lever or zoom button or the like becomes off; if the first and second lens groups 11 and 12 reach a position in front of a predetermined amount from the telephoto position in the drive from the wide angle to the telephoto; and if the first and second lens groups 11 and 12 reach a position in front of a predetermined amount from the wide angle position in the drive from the telephoto to the wide angle.

If the first and second lens groups 11 and 12 are to be stopped, whether the third lens group 13 is driving is judged (step S15). If the third lens group 13 is stopping, the stopping operation of the first and second lens groups 11 and 12 is executed (step S16) and the breaking operation of the first and second lens groups 11 and 12 is executed (step S17). Subsequently, the driving direction of the changing magnification is determined (step S18). If it is the changing magnification from the wide angle to the telephoto, drive for correcting a position of the third lens group 13 is achieved (step S19), the drive of the aperture stop is executed (step S20), and the process is completed and returned from the step S20 to a process waiting state.

If it is determined that the retire process of the fourth lens group 14 is determined to be required in the step S11, the retire process of the fourth lens group 14 is executed (step S21), and the process is shifted from the step S21 to the step S12. In the step S12, if it is determined that the changing magnification driving direction is the changing magnification from the telephoto to the wide angle, the retire process of the third lens group 13 is executed (step S22), and the process is shifted from the step S22 to the step S14.

In the step S14, if it is determined that the first and second lens groups 11 and 12 continue to drive without stopping them, whether the third lens group 13 is driving is judged (step S23). If the third lens group 13 is stopping, whether the drive of the third lens group 13 is initiated is determined (step S24).

It is determined in the step S24 that the drive of the third lens group 13 is permitted in a case satisfying one of conditions in which: if the first and second lens groups 11 and 12 are driven more than the specified driven amount after the initiation of the drive of the first and second lens groups 11 and 12; if the position of the third lens group 13 is away by a predetermined amount or more from the position of the first and second lens groups 11 and 12 when the first and second lens groups 11 and 12 pass a predetermined zooming point in the driving state that the third lens group 13 is re-driven from the wide angle to the telephoto; and if the position of the third lens group 13 is approaching a predetermined amount or more to the position of the first and second lens groups 11 and 12 when the first and second lens groups 11 and 12 pass a predetermined zooming point in the driving state that the third lens group 13 is re-driven from the telephoto to the wide angle.

If the drive of the third lens group 13 is permitted in the step S24, the drive of the third lens group 13 is initiated (step S25), and the process is returned from the step S25 to the step S14. If the drive of the third lens group 13 is not permitted in the step S24, the process is returned from the step S24 to the step S14 directly.

In the step S23, if it is judged that the third lens group 13 is driving, whether the drive of the third lens group 13 is stopped is determined (step S26). It is determined in the step S26 that the third lens group 13 is permitted in a case satisfying one of conditions in which: if the position of the third lens group 13 approaches a predetermined amount or more to the position of the first and second lens groups 11 and 12 in the drive from the wide angle to the telephoto; and if the position of the third lens group 13 is away a predetermined or more from the position of the first and second lens groups 11 and 12 in the drive from the telephoto to the wide angle.

If the stop of the third lens group 13 is permitted in the step S26, the stop of the third lens group 13 is initiated (step S27), and the process is returned from the step S27 to the step S14. In the step S26, if the stop of the third lens group 13 is not permitted, the process is returned the step S26 to the step S14 directly.

In the step S15, if it is judged that the third lens group 13 is driving, the stop of the third lens group 13 is initiated (step S28), and the process is shifted from the step S28 to the step S16. In the step S18, if it is determined that the changing magnification driving direction is the changing magnification from the telephoto to the wide angle, a backlash operation is executed (step S29), and the process is shifted from the step S29 to the step S19.

Next, a changing magnification operation according to the flow chart is explained in detail with reference to each of the direction of changing magnification.

[From Wide Angle to Telephoto]

First, a changing magnification operation from the wide angle to the telephoto is described by referring to the timing chart shown in FIG. 27.

By pressing down a telephoto button of the zoom button, the telephoto switch signal changes from H to L, and thus a variable sequence to the telephoto direction is initiated. Initially, a retire determination of the fourth lens group 14 is executed (step S11).

As described above, in the retire determination of the fourth lens group 14, the fourth lens group 14 is retired only if both of the following conditions are satisfied (AND condition).

(1) Changing magnification drive from telephoto to the wide angle.

(2) The fourth lens group 14 is positioned in a nearer position to the subject (extended out position) away from a predetermined position (retired threshold position).

However, because the above-mentioned conditions are not satisfied in the drive from the wide angle to the telephoto, the fourth lens group 14 is not retired.

Next, in the driving direction, whether the third lens group 13 is to be retired is determined (step S12). In the case of the changing magnification drive from the wide angle to the telephoto, the retiring drive of the third lens group 13 is not necessary. The drive of the first and second lens groups 11 and 12 is initiated through the first and second frames DC motor 503 (step S13).

In an activating period immediately after the initiation of activation of the first and second frames DC motor 503, the drive voltage is set to be lower than the stationary voltage in order to prevent the rush current by the first and second group DC motor. After the activation period is lapsed, the drive voltage is increased to the stationary voltage.

The drive voltage between the wide angle and the telephoto is set to be lower than that between the collapsed position and wide angle position. This is for the reason that a higher speed is required between the stored and wide angle positions, and hence a higher voltage is set, while a suitable voltage setting is made between the wide angle and the telephoto so as to allow the first and second frames DC motor 503 to stop at a desired position by operation of the zoom button.

The control of the movement amount of the first and second lens groups 11 and 12 is achieved by counting the pulse-like signal (PI signal) by the first and second frames photo-interrupter 509. The zooming points each of which is a control reference position are set in 17 points in which a distance between the wide angle and the telephoto is divided into 16 equally.

Next, whether the first and second lens groups 11 and 12 are to be stopped is determined (step S14). In the determination for stopping the drive of the first and second lens groups 11 and 12, if either one of the following conditions is satisfied (OR condition), a stopping process is executed.

(1) A telephoto zooming drive switch operated by the changing magnification operation through the zoom lever or zoom button or the like is turned off, i.e. changed from L to H.

(2) The first and second lens groups 11 and 12 reach a position in front of the telephoto position when driving from the wide angle to the telephoto.

In a case that the driving of the first and second lens groups 11 and 12 is continuing, the judgment of driving initiation/driving stop of the third lens group 13 is executed in response to the status (during driving or stopping) of the third lens group 13 (step S23). If the third lens group 13 is stopping, the determination of drive initiation of the third lens group 13 is executed (step S24), and if the initiation is permitted, the drive of the third lens group 13 is initiated.

In the step S24, the drive of the third lens group 13 is initiated if either one of the following conditions is satisfied.

(1) The first and second lens groups 11 and 12 are driven by the specified driven amount or more after the initiation of the drive of the first and second lens groups 11 and 12.

(2) During the third lens group 13 is re-driving in the drive from the wide angle to the telephoto, the position of the third lens group 13 is away by a predetermined amount from the position of the first and second lens groups 11 and 12 when the first and second lens groups 11 and 12 pass a predetermined zooming point.

Moreover, if the third lens group 13 is driving, whether the third lens group 13 is to be stopped is determined (step S26), and if the stop is permitted, the drive of the third lens group 13 is stopped. In the determination whether the third lens group 13 is to be stopped, the third lens group 13 is stopped if the condition that: the position of the third lens group 13 is positioned closer than the predetermine amount to the position of the first and second lens groups 11 and 12 in the drive from the wide angle to the telephoto, is satisfied.

More specifically, when the first and second lens group 11 and 12 are activated and the driven amount of the first and second lens groups 11 and 12 becomes the specified pulse or more, the drive of the third lens group 13 is initiated. During simultaneous drive of the first, second and third lens groups 11, 12 and 13, if the position of the third lens group 13 approaches by the predetermined amount to the position of the first and second lens groups 11 and 12, the drive of the third lens group 13 is stopped. Thereafter, when the first and second lens groups 11 and 12 are away from the third lens group 13 and they are away from the third lens group 13 by a predetermined amount, the drive of the third lens group 13 is re-started.

The drive and stop of the third lens group 13 are repeated in response to a positional relationship among the first and second lens groups 11 and 12, and the third lens group 13. Thereby, it is possible to achieve the changing magnification drive while maintaining a distance among the first, second, and third lens groups 11, 12 and 13.

When activating these lens groups, the influence of the rush current caused by the first and second frames DC motor 503 can be avoided by initiating the drive of the third lens group 13 after the drive of the specified amount or more of the first and second lens groups 11 and 12 is carried out, and therefore the current consumption is reduced.

If the telephoto switch signal has changed from L to H before the initiation of the initial drive of the third lens group 13, the stop of the first and second lens groups 11 and 12 is controlled without the simultaneous drive of the third lens group 13 therewith. If the first and second lens groups 11 and 12 are stopped after the stop of them is determined, the stop operation of the third lens group 13 is initiated if the third lens group 13 is driving. Then, the stop of the first and second lens groups 11 and 12 is also initiated. A lower speed control period is set during the stop operation of the first and second lens groups 11 and 12, so that the drive voltage of the first and second frames DC motor 503 is lowered according to the residual pulse number to a target position.

Thereby, the overrun amount of the first and second lens groups 11 and 12 when reaching the target position is decreased. If the first and second lens groups 11 and 12 reach the target position by counting the PI signal by the first and second frames photo-interrupter 509, a breaking operation is executed in order to stop the drive of the first and second lens groups 11 and 12. The overrun amount during the period of breaking is also counted to decide a final position of the first and second lens groups 11 and 12.

After the first and second lens groups 11 and 12 are stopped, a correction drive for the position of the third lens group 13 is executed. This is to compute a stopping position of the third lens group 13 corresponding to the final stopping position of the first and second lens groups 11 and 12 and drive the third lens group 13 to the stopping position. A target stopping position of the third lens group 13 corresponding to the stopping position of the first and second lens groups 11 and 12 is interpolatively computed from the positional information of the first and second lens groups 11 and 12 every the zooming point and the positional information of the third lens group 13 every the zooming point. Thereafter, the drive of the aperture stop is achieved to set a position of the aperture stop corresponding to the stopped zooming position of the third lens group 13 (step S20).

[From the Telephoto to the Wide Angle]

Next, a changing magnification operation from the telephoto to the wide angle is described with reference to the timing chart shown in FIG. 28.

By pressing down a wide angle button of the zoom button, the wide angle switch signal changes from H to L, and a variable sequence with respect to the wide angle direction is initiated. Initially, a retire determination of the fourth lens group 14 is executed.

As described above, in the retire determination of the fourth lens group 14, the fourth lens group is retired only if both of the following conditions are satisfied (AND condition).

(1) Changing magnification drive from telephoto to the wide angle.

(2) The fourth lens group 14 is positioned in a closer position to the subject (extended out position) away from a predetermined position (retired threshold position).

If the position of the fourth lens group 14 is in the nearer position than the predetermined position when driving from the telephoto to the wide angle, the fourth lens group 14 is retired. The retired amount is set to a range in which the third lens group 13 does not interfere with the fourth lens group 14 in the variable operation of the third lens group 13.

Next, the third lens group 13 is retired. In order to prevent the interference of the third lens group 13 with the first and second lens groups 11 and 12 due to the initiation of the drive of the first and second lens groups 11 and 12, the third lens group 13 is driven previously by the specified amount. The drive of the first and second lens groups 11 and 12 is then initiated through the first and second frames DC motor 503.

As described above, in the activation period immediately after the initiation of activation of the first and second frames DC motor 503, the drive voltage is set to be lower than the stationary voltage in order to prevent the rush current by the first and second frames DC motor 503. After the activation period is lapsed, the drive voltage is increased to the stationary voltage.

The control of the movement amount of the first and second lens groups 11 and 12 is achieved by counting the pulse-like signal (PI signal) by the first and second frames photo-interrupter 509. As described above, the zooming points each of which is a control reference position are set in 17 points in which a distance between the wide angle and the telephoto is divided into 16 equally.

In the determination for stopping the drive of the first and second lens groups 11 and 12, if either one of the following conditions is satisfied (OR condition), the stopping process is executed, as described above.

(1) A telephoto zooming drive switch operated by the changing magnification operation through the zoom lever or zoom button or the like is turned off, i.e., changed from L to H.

(2) The first and second lens groups 11 and 12 reach a position in front of the telephoto position when driving from the telephoto to the wide angle.

In a case that the driving of the first and second lens groups 11 and 12 is continuing, the determination of driving initiation/driving stop of the third lens group 13 is executed in response to the status (during driving or stopping) of the third lens group 13. If the third lens group 13 is stopping, the determination for the initiation of drive of the third lens group 13 is executed, and if the initiation is permitted, the drive of the third lens group 13 is initiated. In the determination for initiating the drive of the third lens group 13, the drive of the third lens group 13 is initiated if either one of the following conditions is satisfied (OR condition).

(1) The first and second lens groups 11 and 12 are driven by the specified driven amount or more after the initiation of the drive of the first and second lens groups 11 and 12.

(2) During the third lens group 13 is re-driving in the drive from the telephoto to the wide angle, and the position of the third lens group 13 approaches by a predetermined amount to the position of the first and second lens groups 11 and 12 when the first and second lens groups 11 and 12 pass a predetermined zooming point.

Moreover, if the third lens group 13 is driving, the determination for stopping the drive of the third lens group 13 is executed, and if the stop is permitted, the drive of the third lens group 13 is stopped. In the determination whether the third lens group 13 is to be stopped, the third lens group 13 is stopped if the condition that: the position of the third lens group 13 is away by the predetermine amount or more from the position of the first and second lens groups 11 and 12 in the drive from the telephoto to the wide angle, is satisfied.

More specifically, the first and second lens group 11 and 12 are activated, and if the driven amount of the first and second lens groups 11 and 12 becomes the specified amount or more, the drive of the third lens group 13 is initiated. During simultaneous drive of the first, second and third lens groups 11, 12 and 13, if the position of the third lens group 13 is away by the predetermined amount from the position of the first and second lens groups 11 and 12, the drive of the third lens group 13 is stopped. Thereafter, when the first and second lens groups 11 and 12 approach to the third lens group 13 and approach to the third lens group 13 by the specified amount or more, the drive of the third lens group 13 is re-started.

The drive and stop of the third lens group 13 are repeated in response to a positional relationship among the first and second lens groups 11 and 12, and the third lens group 13. Thereby, it is possible to achieve the changing magnification drive while maintaining a distance among the first, second, and third lens groups 11, 12, and 13. In addition, the influence of the rush current of the first and second frames DC motor 503 can be avoided by initiating the drive of the third lens group 13 after the specified pulse or more is counted from the activation of the first and second lens groups 11 and 12. Thereby, it is possible to reduce the current consumption.

In the drive of the third lens group 13 to the wide angle direction during the drive of the first and second lens groups 11 and 12, basically a control for eliminating a backlash in the movement of the third lens group 13 is required when it is stopped. However, the backlash eliminating control is not carried out (or prohibited) during the changing magnification operation so as to accomplish a smooth movement of the third lens group 13.

If the wide angle switch signal has changed from L to H before the initiation of the initial drive of the third lens group 13, the stop of the first and second lens groups 11 and 12 is controlled without the simultaneous drive of the third lens group 13 therewith. If the first and second lens groups 11 and 12 are stopped after the stop of them is determined, the stop operation of the third lens group 13 is initiated if the third lens group 13 is driving. Then, the stop of the first and second lens groups 11 and 12 is also initiated.

During the stop operation of the first and second lens groups 11 and 12, a lower speed control period is set. Accordingly, the drive voltage of the first and second frames DC motor 503 is lowered based on the residual pulse number to a target position. Thereby, the overrun amount of the first and second lens groups 11 and 12 when reaching the target position is decreased.

If the first and second lens groups 11 and 12 reach the target position by counting the PI signal by the first and second frames photo-interrupter 509, a breaking operation is executed in order to stop the drive of the first and second lens groups 11 and 12. The overrun amount during the period of breaking is also counted to decide a final position of the first and second lens groups 11 and 12.

Furthermore, the control for eliminating the backlash of the first and second lens groups 11 and 12 is executed in the movement from the telephoto to the wide angle thereof.

After the first and second lens groups 11 and 12 are stopped, a correction drive for the position of the third lens group 13 is executed. This is to compute the stopping position of the third lens group 13 corresponding to the final stopping position of the first and second lens groups 11 and 12 and drive the third lens group 13 to the stopping position. A target stopping position of the third lens group 13 corresponding to the stopping position of the first and second lens groups 11 and 12 is interpolatively computed from the positional information of the first and second lens groups 11 and 12 every the zooming point and the positional information of the third lens group 13 every the zooming point. In the drive in the wide angle direction of the third lens group 13, the control for eliminating the backlash of the third lens group 13 is executed after it is stopped. Thereafter, the drive of the aperture stop is achieved so that the aperture stop is disposed in a position corresponding to the stopped zooming position of the third lens group 13.

In this example, the drive voltage of the first and second frames DC motor 503 when it is driven in the wide angle direction is set to be higher than that in the telephoto direction in the changing magnification operation between the wide angle and the telephoto. The pulse rate of the third frame pulse motor 507 in the wide angle direction is set to be faster than that in the telephoto direction. An intermittent control for the third lens group 13 is accomplished based on the positional relationship among the first, second, and third lens groups 11, 12, and 13 in order to maintain the distance among the first, second, and third lens groups 11, 12, and 13. Therefore, the drive speed of the third lens group 13 is set to be the same as or faster than the drive speed of the first and second lens groups 11 and 12, in the movement in the telephoto direction.

Similarly, the drive speed of the third lens group 13 is also set to be the same as or faster than the drive speed of the first and second lens groups 11 and 12, in the movement in the wide angle direction. With such a structure, the third lens group 13 is driven so that the third lens group 13 is not separated away from the first and second lens groups 11 and 12 in the movement in the telephoto direction, and does not caught up by the first and second lens groups 11 and 12 in the movement in the wide angle direction.

In the above-mentioned embodiments, the structure in which the third lens group 13 is retracted out the lens cylinder unit transverse to the optical axis X has been described. In this structure, the retracted third lens group 13 has the minimum outer diameter. When the third lens group 13 having the minimum outer diameter is retracted, a projective size of the lens barrel in which the third lens group 13 is retracted can be minimized efficiently, and thus the thickness of the lens barrel can be reduced.

Moreover, when the retracted lens is extended out of the fixed frame, a size of the device (lead screw and so on) for driving the retired lens group (i.e. the third lens group) is minimized by taking a structure such that the retracted lens is not away from the imaging plane possibly.

Furthermore, the lens retaining frame of the third lens group 13 or the third lens group 13 itself is larger than the lens retaining frames of the other lens groups 11, 12, 14 or the other lens groups 11, 12, 14 in length along the optical axis X, i.e., thickness. When the thickness of the third lens group 13 is larger than that of the other lens groups 11, 12, and 14, consequently, the thickness of the other lens groups decreases. Therefore, the thickness of the lens barrel can be reduced when the lens barrel is in the collapsed position. As a result, the thickness of the lens barrel or a size in the direction of the optical axis of the lens barrel is minimized.

In addition, because the retract lens group or the third lens group 13 is disposed behind and adjacent the shutter having the aperture stop function, the diameter of the lens barrel is less, and the retraction of the third lens group 13 is simplified without considering the interference of the shutter with the lens group unit and separating the position of the shutter from the lens cylinder unit, excessively.

Next, a structure of the plurality of lens groups is explained in further detail. Note that the following structure or arrangement of the plurality of lens groups is exemplary, and that the structure or arrangement of the plurality of lens groups may be appropriately modified.

The first lens group 11 has a positive power, the second lens group 12 has a negative power, the third lens group 13 has a positive power, and the fourth lens group 14 has a positive power. A changing magnification operation is achieved by changing at least one of intervals between the first and second lens groups 11 and 12, between the second and third lens groups 12 and 13, and between the third and fourth lens groups 13 and 14. A focusing operation is achieved by moving the fourth lens group 14 along the optical axis X.

The shutter/aperture unit 15 is disposed between the second lens group 12 and the third lens group 13. In other words, the shutter having the function of the aperture stop is positioned in front of the third lens group 13.

The four lens groups are provided in the lens cylinder unit. Because the third lens group having the minimum outer diameter is retracted out of the lens cylinder unit without separating from the image plane excessively, the retraction of the third lens group 13 can be accomplished with the minimum movement and the outer diameter of the lens barrel can be minimized. In addition, the thickness of the lens barrel is decreased by retraction of at least one lens group.

Furthermore, it is possible to provide a compact lens barrel having a high changing magnification ratio, 4 times or more.

Meanwhile, the lens groups may be structured from a first lens group having a positive power, a second lens group having a negative power, and a third lens group having a positive power, and the third lens group may be retracted.

Alternatively, the lens groups may be structured by a first lens group having a negative power, a second lens group having a positive power, and a third lens group having a positive power, and the second lens group or the third lens group may be retracted.

Each of the lens groups may be structured from one or more lenses, and the lens groups herein indicate integral one or more lenses. Therefore, all the lens groups may be structured by one lens, respectively.

Referring now to FIG. 17A to FIG. 19, a camera including an optical system device having the lens barrel according to the present invention as shown in the first embodiment will be described as a second embodiment.

Although the lens barrel is applied to the camera here, the lens barrel is also applicable to a lens driving apparatus, an optical device, etc. In addition, the lens barrel according to the present invention as shown in the first embodiment is also applicable to a mobile information terminal such as so-called PDA (Personal Data Assistant), a mobile phone and so on, having a camera function or functional part installed therein.

Many of such mobile information terminals have the function and the structure substantially identical to the function and the structure of the camera, although the appearance is slightly different. Therefore, the optical system device including the lens barrel according to the present invention may be employed in such mobile information terminals. Further, the lens barrel according to the present invention may be applied to an image forming device such as a copying machine, a scanner or the like.

As shown in FIG. 17A, FIG. 17B and FIG. 18, the camera includes an image pickup lens 101, a shutter release button 102, a zoom lever 103, a viewfinder 104, a strobe light 105, a liquid crystal display (LCD) 106, an operating button 107, a power switch 108, a memory card slot 109, an expansion card slot 110, the barrier-operating element 301 and so on.

Furthermore, as shown in FIG. 19, the camera also includes a photodetector 201, a signal-processing unit 202, an image-processing unit 203, a central processing unit (CPU) 204, a semiconductor memory 205, and an expansion card 206. Although it is not shown specifically, electric power is supplied from a battery as an electric source to the above-mentioned parts to operate the parts.

The photodetector 201 serves as an area sensor such as a CCD (Charge Coupled Device) image pickup element or the like to read an image of a subject to be photographed, that is, of an photographing subject, formed by the image pickup lens 101, which is a photographing optical system. As the image pickup lens 101, the optical system device including the lens barrel according to the present invention as described in the first embodiment is employed.

More specifically, the optical system device includes a plurality lens groups as optical elements and a telescopic cylinder unit retaining the lens groups, which structure the lens barrel.

The lens barrel has a mechanism of retaining the respective lens groups in the lens cylinder such that the lens groups can be moved in response to the movement of the lens cylinder along the optical axis of the lens groups, similarly to the above-mentioned embodiment. The image pickup lens 101 to be integrated in the camera is generally integrated in the form of this optical system device.

An output from the photodetector 201 is processed by the signal-processing unit 202, which is controlled by the central processing unit 204, and is converted into digital image information. The image information digitized by the signal-processing unit 202 is subjected to a predetermined image processing in the image-processing unit 203 which is also controlled by the central processing unit 204, and then stored in the semiconductor memory 205 such as a non-volatile memory.

In this case, the semiconductor memory 205 may be a memory card inserted in the memory card slot 109, or may be a semiconductor memory integrated in a body of the camera. The liquid crystal display 106 may display the photographing image or may display the image stored in the semiconductor memory 205. An image stored in the semiconductor memory 205 can be transmitted to the outside of the camera via the expansion card 206 inserted in the expansion card slot 110. Meanwhile, the above-mentioned central calculation processing device 501 shown in FIG. 21 to control the drive of the lens groups may be included in the central processing unit 204, otherwise structured by use of other micro-processor connecting with the central calculation processing device 501.

The image pickup lens 101 is embedded within the camera body into a collapsed or stored state as shown in FIG. 17A when being transported or carried by a user, and the lens barrier 62 is closed. When the user operates the barrier-operating element 301 to open the lens barrier 62, the power is turned on and the lens barrel is moved from the closed position to an opened position and projected from the camera body as shown in FIG. 17B, so that the photographing state is established. At this time, the image pickup lens 101 within the lens barrel is set so that the respective lens groups of the optical systems structuring a zoom lens are arranged, for example, at a short focal length wide angle position.

When the zoom lever 103 is operated, the arrangement of the respective lens groups in the optical system is changed through the movement of the lens groups along the optical axis, and therefore, the zoom can be varied to the telephoto position.

Preferably, an optical system of the viewfinder 104 is configured such that the zooming is varied in association with the change of the angle of field of the image pickup lens 101.

In many cases, focusing is achieved by half-pressing operation of the shutter release button 102. The focusing with the zoom lens in the lens barrel according to the present invention is achieved mainly by moving the fourth lens group 14, although it is not limited thereto. When the shutter release button 102 is further pressed to a completely pressed state, the photographing is achieved, and subsequently the processing as described above is performed.

In order to display the image stored in the semiconductor memory 205 on the liquid crystal display 106 or transmit the same to the outside of the camera via the expansion card 206, the operating button 107 is operated in a predetermined manner. The semiconductor memory 205 and the communication card 206 or the like are used by being inserted in a specific or multi-purpose slot such as the memory card slot 109 and the communication car slot 110.

When the image pickup lens 101 is in the stored state, the third lens group 13 is retracted from the optical axis to the retracted position outside of the telescopic cylinder unit, and hence is stored in a line with the first lens group 11 and the second lens group 12 in a juxtaposed manner. Therefore, further reduction in thickness of the camera is achieved.

Generally, because a viewfinder mechanism is disposed above of the lens barrel, therefore, certain camera operation is easy. Moreover, if the lens barrel includes a zoom changing magnification mechanism, because the viewfinder mechanism also needs the zoom changing magnification mechanism, it is preferable that a drive source (DC motor, pulse motor or the like) for conducting the zoom changing magnification operation and a transmission mechanism (gear connecting mechanism or the like) for transferring a driving force of the drive source to the lens groups are disposed adjacent the viewfinder mechanism. For example, if the viewfinder mechanism is disposed on upper and left position of the lens barrel, the drive source and the transmission mechanism are disposed adjacent the upper and left position of the lens barrel to use a limited space effectively.

When the frame for the retractable lens group (third lens group 13 according to the embodiment) is retracted, the retaining frame is stored below the lens barrel in consideration of the left space. The space is lower and right position or lower and left position of the lens barrel. In the embodiment, the space is disposed on the lower and right position of the lens barrel to store the retaining frame of the retracted third lens group. The above-mentioned storage part of the fixed lens cylinder is disposed at the position.

The drive source and the transmission mechanism for driving the lens groups are disposed at the lower and left position. As a result, a miniaturized lens barrel can be accomplished with effective use of fourth corners, the upper and left position, the upper and right position, the lower and right position, and the lower and left position of a lens barrel.

Although the present invention has been described in terms of exemplary embodiments, it is not limited thereto. It should be appreciated that variations may be made in the embodiments described by persons skilled in the art without departing from the scope of the present invention as defined by the following claims. Moreover, no element and component in the present disclosure is intended to be dedicated to the public regardless of whether the element or component is explicitly recited in the following claims.

INDUSTRIAL APPLICABILITY

The lens barrel according to the present invention is applicable to any portable device having a camera function or functional part installed therein. The example of which is a mobile information terminal such as so-called PDA (Personal Data Assistant), a mobile phone, and so on although it is not limited thereto. The lens barrel according to the present invention may also be applied to an image forming device such as a copying machine, a scanner and so on, and to a lens driving apparatus and an optical device as well. 

1. A lens barrel, comprising: a) a plurality of lens groups each having at least one lens; b) a plurality of lens retaining frames each retaining corresponding one of the plurality of lens groups; c) a telescopic cylinder containing therein the plurality of lens groups and the plurality of lens retaining frames; d) a lens retaining frame driving device configured to drive at least one of the lens retaining frames; at least one portion of the plurality of lens groups being collapsed to store the plurality of lens groups in a collapsed state and at least one portion of the plurality of lens groups being moved toward a subject in a photographable state, the plurality of lens retaining frames including a retractable lens retaining frame configured to retain and retract at least one of the plurality of lens groups to a retracted position substantially out of the telescopic cylinder in the collapsed state and configured to move the corresponding at least one of the plurality of lens groups from the retracted position to a photographing position in the photographable state such that an optical axis of the corresponding at least one of the plurality of lens groups substantially coincide with an optical axis of the other lens group of the plurality of lens groups in order that all of the plurality of lens groups be substantially aligned on the same optical axis; and e) a position detector configured to detect a change in a position of the retractable lens retaining frame in the collapsed state and in the photographable state, the retractable lens retaining frame including a cam portion configured to change a position of the retractable lens retaining frame between the retracted position which is substantially out of the telescopic cylinder and which is distant from the optical axis of said the other lens group, and the photographing position in which the optical axis of the corresponding at least one of the plurality of lens groups retained by the retractable lens retaining frame is positioned substantially on the optical axis of said the other lens group and in which the retractable lens retaining frame is moveable in a direction substantially coaxial with the optical axis of said the other lens group, so as to detect, based on an amount of a displacement of the retractable lens retaining frame in the direction substantially coaxial with the optical axis of said the other lens group, a displacement of the retractable lens retaining frame in a direction in which the optical axis of the corresponding at least one of the plurality of lens groups retained by the retractable lens retaining frame approaches and separates away from the optical axis of said the other lens group between the collapsed state and the photographable state, and a displacement of the retractable lens retaining frame in the direction substantially coaxial with the optical axis of said the other lens group in the photographable state, the lens retaining frame driving device including a lead screw configured to advance and retreat the retractable lens retaining frame in a direction substantially extending parallel with the optical axis of said the other lens group, and a female screw member screwed on the lead screw and capable of being advanced and retracted by rotation of the lead screw in an axial direction of the lead screw which extends substantially in parallel with the optical axis of said the other lens group, the female screw member including a contact portion configured to contact with the cam portion to change the position of the retractable lens retaining frame between the retracted position and the photographing position by the rotation of the lead screw, and the position detector including a detected portion provided on the female screw member so as to detect the position of the female screw member in the axial direction at the time of the rotation of the lead screw, and a detecting portion arranged in an area of movement of the detected portion for detecting a displacement of the detected portion in the axial direction.
 2. The lens barrel according to claim 1, wherein the position detector is configured to generate a reference signal indicating that the retractable lens retaining frame is located at the retracted position so as to change a state of the retractable lens retaining frame from the collapsed state to the photographable state, before moving the retractable lens retaining frame from the retracted position to the photographing position so as to substantially coincide the optical axis of the corresponding at least one of the plurality of lens groups retained by the retractable lens retaining frame with the optical axis of said the other lens group.
 3. The lens barrel according to claim 1, wherein the position detector is configured to generate an entering completed signal indicating that entering of the optical axis of the corresponding at least one of the plurality of lens groups retained by the retractable lens retaining frame on the optical axis of said the other lens group from the retracted position to the photographing position has completed, after the state of the retractable lens retaining frame has changed from the collapsed state to the photographable state.
 4. The lens barrel according to claim 1, wherein the position detector is configured to output a positional reference signal in an optical axis direction so as to displace the retractable lens retaining frame in the direction substantially coaxial with the optical axis of said the other lens group for performing photographing, after the optical axis of the corresponding at least one of the plurality of lens groups retained by the retractable lens retaining frame has approached on the optical axis of said the other lens group from the retracted position to the photographing position.
 5. The lens barrel according to claim 3, further comprising at least one optical element located nearer to an image plane in the lens barrel than the retractable lens retaining frame, wherein the position detector permits movement of the optical element after generating the entering completed signal of the retractable lens retaining frame at the time when the state of the retractable lens retaining frame has transited from the collapsed state to the photographable state.
 6. The lens barrel according to claim 1, wherein the detected portion is substantially in an alphabet T configuration.
 7. The lens barrel according to claim 1, wherein the detected portion is substantially in an alphabet L configuration.
 8. A lens driving apparatus, comprising the lens barrel according to claim
 1. 9. A camera, comprising the lens barrel according to claim
 1. 10. A mobile information terminal, comprising the lens barrel according to claim
 1. 